Unexplained Mysteries of The World #4 UFOs and Area 51 The first reported UFO sighting happened in Texas in 1878, when a local farmer reported seeing a large, dark, circular flying object flying "at wonderful speed". Another famous early sighting occurred in the UK in 1916, when a pilot reported seeing a row of lights that rose and disappeared into the sky. After UFOs were popularized by science fiction in the 1950s, the number of sightings went through the roof. (About a decade before the first UFO-crop circle sighting was reported.) Theories to explain the paranormal phenomena range from the good old Extraterrestrial Hypothesis (aliens visiting us from another planet) to the Interdimensional Hypothesis (aliens popping over from a parallel universe). Although I do believe there is other life out there in the universe (and tons of it - the universe is so mind-bogglingly huge) I don't believe aliens are visiting us in flying saucers, nor making crop circles just to freak us out. The truth is that UFO sightings can be explained as airplanes, helicopters, weather balloons, comets, meteors and even the five planets which can be seen with the naked eye. In photos and videos they are usually deemed as dust on the camera lens or simply all-out hoaxes (which is ridiculously easy to do now with PhotoShop). Meanwhile, night-time alien visitations can be explained by the hallucinogenic effect of the sleep disorder Sleep Paralysis. Meanwhile, UFO conspiracy theories center around Area 51 in Nevada, about 90 miles north of Las Vegas. The site houses a large air base that was selected in the 1950s for testing of a U-2 spy plane. It has since become America's testing ground for secret "black budget" aircraft before they go public.

Unexplained Mysteries of The World #3 Bigfoot (aka Sasquatch) He's big, he's hairy, and he's starred in his own TV show. Bigfoot is world-famous for spooking the bejesus out of hikers and hunters in North America. Scientists consider Sasquatch to be the result of folklore, misidentification and a whole lot of hoaxes. However, many people still believe these humanoid creatures exist around the world, just like the Yeti of the Himalayas. One of the most infamous unexplained mysteries in the world today, Bigfoot has been described as an ape-like creature, some 6-10 feet tall, weighing more than 500 pounds, and covered in dark brown or reddish hair. Witnesses give him large eyes, a heavy brow ridge and a crested head, much like a male gorilla. Footprints allegedly belonging to Bigfoot are 24 inches long. Is Sasquatch really one of the great truly unexplained mysteries of the world? Somewhat disappointingly, the most famous footage of Bigfoot at Bluff Creek, California, was shot down by a man called Bob Heironimus. Years after the event, he claimed he wore an ape costume for the filming. It's also virtually impossible that a prehistoric, bipedal, apelike creature could exist, simply because the breeding population of such an animal would have to be so large that many more sightings would be reported. What's more, with so many bigfoots running around, we would have found some physical evidence by now, such as fecal matter, hair, footprints, and even numerous corpses and skeletons. Nevertheless, Bigfoot's cousin - the Yeti (aka the Abominable Snowman) - has a strong alleged presence in the Himalayan regions of Nepal and Tibet. Teams of scientists continue to seek out photo evidence which is also thin on the ground - yet many locals accept the reality of a breeding Yeti population as read.

cceleration The final mathematical quantity discussed in Lesson 1 is acceleration. An often confused quantity, acceleration has a meaning much different than the meaning associated with it by sports announcers and other individuals. The definition of acceleration is: Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity. Sports announcers will occasionally say that a person is accelerating if he/she is moving fast. Yet acceleration has nothing to do with going fast. A person can be moving very fast and still not be accelerating. Acceleration has to do with changing how fast an object is moving. If an object is not changing its velocity, then the object is not accelerating. The data at the right are representative of a northward-moving accelerating object. The velocity is changing over the course of time. In fact, the velocity is changing by a constant amount - 10 m/s - in each second of time. Anytime an object's velocity is changing, the object is said to be accelerating; it has an acceleration. The Meaning of Constant Acceleration Sometimes an accelerating object will change its velocity by the same amount each second. As mentioned in the previous paragraph, the data table above show an object changing its velocity by 10 m/s in each consecutive second. This is referred to as a constant acceleration since the velocity is changing by a constant amount each second. An object with a constant acceleration should not be confused with an object with a constant velocity. Don't be fooled! If an object is changing its velocity -whether by a constant amount or a varying amount - then it is an accelerating object. And an object with a constant velocity is not accelerating. The data tables below depict motions of objects with a constant acceleration and a changing acceleration. Note that each object has a changing velocity. Since accelerating objects are constantly changing their velocity, one can say that the distance traveled/time is not a constant value. A falling object for instance usually accelerates as it falls. If we were to observe the motion of a free-falling object (free fall motion will be discussed in detail later), we would observe that the object averages a velocity of approximately 5 m/s in the first second, approximately 15 m/s in the second second, approximately 25 m/s in the third second, approximately 35 m/s in the fourth second, etc. Our free-falling object would be constantly accelerating. Given these average velocity values during each consecutive 1-second time interval, we could say that the object would fall 5 meters in the first second, 15 meters in the second second (for a total distance of 20 meters), 25 meters in the third second (for a total distance of 45 meters), 35 meters in the fourth second (for a total distance of 80 meters after four seconds). These numbers are summarized in the table below. Time Interval Ave. Velocity During Time Interval Distance Traveled During Time Interval Total Distance Traveled from 0s to End of Time Interval 0 - 1 s ~ 5 m/s ~ 5 m ~ 5 m 1 -2 s ~ 15 m/s ~ 15 m ~ 20 m 2 - 3 s ~ 25 m/s ~ 25 m ~ 45 m 3 - 4 s ~ 35 m/s ~ 35 m ~ 80 m Note: The ~ symbol as used here means approximately. This discussion illustrates that a free-falling object that is accelerating at a constant rate will cover different distances in each consecutive second. Further analysis of the first and last columns of the data above reveal that there is a square relationship between the total distance traveled and the time of travel for an object starting from rest and moving with a constant acceleration. The total distance traveled is directly proportional to the square of the time. As such, if an object travels for twice the time, it will cover four times (2^2) the distance; the total distance traveled after two seconds is four times the total distance traveled after one second. If an object travels for three times the time, then it will cover nine times (3^2) the distance; the distance traveled after three seconds is nine times the distance traveled after one second. Finally, if an object travels for four times the time, then it will cover 16 times (4^2) the distance; the distance traveled after four seconds is 16 times the distance traveled after one second. For objects with a constant acceleration, the distance of travel is directly proportional to the square of the time of travel. Calculating the Average Acceleration The average acceleration (a) of any object over a given interval of time (t) can be calculated using the equation This equation can be used to calculate the acceleration of the object whose motion is depicted by the velocity-time data table above. The velocity-time data in the table shows that the object has an acceleration of 10 m/s/s. The calculation is shown below. Acceleration values are expressed in units of velocity/time. Typical acceleration units include the following: m/s/s mi/hr/s km/hr/s m/s2 These units may seem a little awkward to a beginning physics student. Yet they are very reasonable units when you begin to consider the definition and equation for acceleration. The reason for the units becomes obvious upon examination of the acceleration equation. Since acceleration is a velocity change over a time, the units on acceleration are velocity units divided by time units - thus (m/s)/s or (mi/hr)/s. The (m/s)/s unit can be mathematically simplified to m/s2. The Direction of the Acceleration Vector Since acceleration is a vector quantity, it has a direction associated with it. The direction of the acceleration vector depends on two things: whether the object is speeding up or slowing down whether the object is moving in the + or - direction The general RULE OF THUMB is: If an object is slowing down, then its acceleration is in the opposite direction of its motion. This RULE OF THUMB can be applied to determine whether the sign of the acceleration of an object is positive or negative, right or left, up or down, etc. Consider the two data tables below. In each case, the acceleration of the object is in the positive direction. In Example A, the object is moving in the positive direction (i.e., has a positive velocity) and is speeding up. When an object is speeding up, the acceleration is in the same direction as the velocity. Thus, this object has a positive acceleration. In Example B, the object is moving in the negative direction (i.e., has a negative velocity) and is slowing down. According to our RULE OF THUMB, when an object is slowing down, the acceleration is in the opposite direction as the velocity. Thus, this object also has a positive acceleration. This same RULE OF THUMB can be applied to the motion of the objects represented in the two data tables below. In each case, the acceleration of the object is in the negative direction. In Example C, the object is moving in the positive direction (i.e., has a positive velocity) and is slowing down. According to our RULE OF THUMB, when an object is slowing down, the acceleration is in the apposite direction as the velocity. Thus, this object has a negative acceleration. In Example D, the object is moving in the negative direction (i.e., has a negative velocity) and is speeding up. When an object is speeding up, the acceleration is in the same direction as the velocity. Thus, this object also has a negative acceleration. Observe the use of positive and negative as used in the discussion above (Examples A - D). In physics, the use of positive and negative always has a physical meaning. It is more than a mere mathematical symbol. As used here to describe the velocity and the acceleration of a moving object, positive and negative describe a direction. Both velocity and acceleration are vector quantities and a full description of the quantity demands the use of a directional adjective. North, south, east, west, right, left, up and down are all directional adjectives. Physics often borrows from mathematics and uses the + and - symbols as directional adjectives. Consistent with the mathematical convention used on number lines and graphs, positive often means to the right or up and negative often means to the left or down. So to say that an object has a negative acceleration as in Examples C and D is to simply say that its acceleration is to the left or down (or in whatever direction has been defined as negative). Negative accelerations do not refer acceleration values that are less than 0. An acceleration of -2 m/s/s is an acceleration with a magnitude of 2 m/s/s that is directed in the negative direction. Check Your Understanding To test your understanding of the concept of acceleration, consider the following problems and the corresponding solutions. Use the equation for acceleration to determine the acceleration for the following two motions.

Black holes aren’t black

They’re very dark, sure, but they aren’t black. They glow, slightly, giving off light across the whole spectrum, including visible light.
This radiation is called “Hawking radiation”, after the former Lucasian Professor of Mathematics at Cambridge University Stephen Hawking, who first proposed its existence. Because they are constantly giving this off, and therefore losing mass, black holes will eventually evaporate altogether if they don’t have another source of mass to sustain them; for example interstellar gas or light.
Smaller black holes are expected to emit radiation faster compared to their mass than larger ones, so if – as some theories predict – the Large Hadron Collider creates minuscule holes through particle collisions, they will evaporate almost immediately. Scientists would then be able to observe their decay through the radiation.
The fundamental description of the universe does not account for a past, present or future
According to the special theory of relativity, there is no such thing as a present, or a future, or a past. Time frames are relative: I have one, you have one, the third planet of Gliese 581 has one. Ours are similar because we are moving at similar speeds.
If we were moving at very different speeds, we would find that one of us aged quicker than the other. Similarly, if one of us was closer than the other to a major gravity well like the Earth, we would age slower than someone who wasn’t.
GPS satellites, of course, are both moving quickly and at significant distances from Earth. So their internal clocks show a different time to the receivers on the ground. A lot of computing power has to go into making your sat-nav work around the theory of special relativity.
A particle here can affect one on the other side of the universe, instantaneously

When an electron meets its antimatter twin, a positron, the two are annihilated in a tiny flash of energy. Two photons fly away from the blast.
Subatomic particles like photons and quarks have a quality known as “spin”. It’s not that they’re really spinning – it’s not clear that would even mean anything at that level – but they behave as if they do. When two are created simultaneously the direction of their spin has to cancel each other out: one doing the opposite of the other.
Due to the unpredictability of quantum behaviour, it is impossible to say in advance which will go “anticlockwise” and the other “clockwise”. More than that, until the spin of one is observed, they are both doing both.
It gets weirder, however. When you do observe one, it will suddenly be going clockwise or anticlockwise. And whichever way it is going, its twin will start spinning the other way, instantly, even if it is on the other side of the universe. This has actually been shown to happen in experiment (albeit on the other side of a laboratory, not a universe).
The faster you move, the heavier you get

Mechanics

Weight (force of gravity) decreases as you move away from the earth by distance squared.
Mass and inertia are the same thing.
Constant velocity and zero velocity means the net force is zero and acceleration is zero.
Weight (in newtons) is mass x acceleration (w = mg). Mass is not weight!
Velocity, displacement [s], momentum, force and acceleration are vectors.
Speed, distance [d], time, and energy (joules) are scalar quantities.
The slope of the velocity-time graph is acceleration.
At zero (0) degrees two vectors have a resultant equal to their sum. At 180 degrees two vectors have a resultant equal to their difference. From the difference to the sum is the total range of possible resultants.
Centripetal force and centripetal acceleration vectors are toward the center of the circle- while the velocity vector is tangent to the circle.
An unbalanced force (object not in equilibrium) must produce acceleration.
The slope of the distance-tine graph is velocity.
The equilibrant force is equal in magnitude but opposite in direction to the resultant vector.
Momentum is conserved in all collision systems.
Magnitude is a term use to state how large a vector quantity is.


Energy

Mechanical energy is the sum of the potential and kinetic energy.
Units: a = [m/sec2], F = [kg•m/sec2] (newton), work = pe= ke = [kg•m2/sec2] (joule)
An ev is an energy unit equal to 1.6 x 10-19 joules
Gravitational potential energy increases as height increases.
Kinetic energy changes only if velocity changes.
Mechanical energy (pe + ke) does not change for a free falling mass or a swinging pendulum. (when ignoring air friction)
The units for power are [joules/sec] or the rate of change of energy.


Electricity

A coulomb is charge, an amp is current [coulomb/sec] and a volt is potential difference [joule/coulomb].
Short fat cold wires make the best conductors.
Electrons and protons have equal amounts of charge (1.6 x 10-19 coulombs each).
Adding a resistor in parallel decreases the total resistance of a circuit.
Adding a resistor in series increases the total resistance of a circuit.
All resistors in series have equal current (I).
All resistors in parallel have equal voltage (V).
If two charged spheres touch each other add the charges and divide by two to find the final charge on each sphere.
Insulators contain no free electrons.
Ionized gases conduct electric current using positive ions, negative ions and electrons.
Electric fields all point in the direction of the force on a positive test charge.
Electric fields between two parallel plates are uniform in strength except at the edges.
Millikan determined the charge on a single electron using his famous oil-drop experiment.
All charge changes result from the movement of electrons not protons (an object becomes positive by losing electrons)


Magnetism

The direction of a magnetic field is defined by the direction a compass needle points.
Magnetic fields point from the north to the south outside the magnet and south to north inside the magnet.
Magnetic flux is measured in webers.
Left hands are for negative charges and right hands are for positive charges.
The first hand rule deals with the B-field around a current bearing wire, the third hand rule looks at the force on charges moving in a B-field, and the second hand rule is redundant.
Solenoids are stronger with more current or more wire turns or adding a soft iron core.


Wave Phenomena

Sound waves are longitudinal and mechanical.
Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher (n) value medium.
All angles in wave theory problems are measured to the normal.
Blue light has more energy. A shorter wavelength and a higher frequency than red light (remember- ROYGBIV).
The electromagnetic spectrum (radio, infrared, visible. Ultraviolet x-ray and gamma) are listed lowest energy to highest.
A prism produces a rainbow from white light by dispersion (red bends the least because it slows the least).
Light wave are transverse (they can be polarized).
The speed of all types of electromagnetic waves is 3.0 x 108 m/sec in a vacuum.
The amplitude of a sound wave determines its energy.
Constructive interference occurs when two waves are zero (0) degrees out of phase or a whole number of wavelengths (360 degrees.) out of phase.
At the critical angle a wave will be refracted to 90 degrees.
According to the Doppler effect a wave source moving toward you will generate waves with a shorter wavelength and higher frequency.
Double slit diffraction works because of diffraction and interference.
Single slit diffraction produces a much wider central maximum than double slit.
Diffuse reflection occurs from dull surfaces while regular reflection occurs from mirror type surfaces.
As the frequency of a wave increases its energy increases and its wavelength decreases.
Transverse wave particles vibrate back and forth perpendicular to the wave direction.
Wave behavior is proven by diffraction, interference and the polarization of light.
Shorter waves with higher frequencies have shorter periods.
Radiowaves are electromagnetic and travel at the speed of light (c).
Monochromatic light has one frequency.
Coherent light waves are all in phase.


Geometric Optics

Real images are always inverted.
Virtual images are always upright.
Diverging lens (concave) produce only small virtual images.
Light rays bend away from the normal as they gain speed and a longer wavelength by entering a slower (n) medium {frequency remains constant}.
The focal length of a converging lens (convex) is shorter with a higher (n) value lens or if blue light replaces red.


Modern Physics

The particle behavior of light is proven by the photoelectric effect.
A photon is a particle of light {wave packet}.
Large objects have very short wavelengths when moving and thus can not be observed behaving as a wave. (DeBroglie Waves)
All electromagnetic waves originate from accelerating charged particles.
The frequency of a light wave determines its energy (E = hf).
The lowest energy state of a atom is called the ground state.
Increasing light frequency increases the kinetic energy of the emitted photo-electrons.
As the threshold frequency increase for a photo-cell (photo emissive material) the work function also increases.
Increasing light intensity increases the number of emitted photo-electrons but not their KE.


Internal Energy

Internal energy is the sum of temperature (ke) and phase (pe) conditions.
Steam and liquid water molecules at 100 degrees have equal kinetic energies.
Degrees Kelvin (absolute temp.) Is equal to zero (0) degrees Celsius.
Temperature measures the average kinetic energy of the molecules.
Phase changes are due to potential energy changes.
Internal energy always flows from an object at higher temperature to one of lower temperature.


Nuclear Physics

Alpha particles are the same as helium nuclei and have the symbol .
The atomic number is equal to the number of protons (2 for alpha)
Deuterium () is an isotope of hydrogen ()
The number of nucleons is equal to protons + neutrons (4 for alpha)
Only charged particles can be accelerated in a particle accelerator such as a cyclotron or Van Der Graaf generator.
Natural radiation is alpha (), beta () and gamma (high energy x-rays)
A loss of a beta particle results in an increase in atomic number.
All nuclei weigh less than their parts. This mass defect is converted into binding energy. (E=mc2)
Isotopes have different neutron numbers and atomic masses but the same number of protons (atomic numbers).
Geiger counters, photographic plates, cloud and bubble chambers are all used to detect or observe radiation.
Rutherford discovered the positive nucleus using his famous gold-foil experiment.
Fusion requires that hydrogen be combined to make helium.
Fission requires that a neutron causes uranium to be split into middle size atoms and produce extra neutrons.
Radioactive half-lives can not be changed by heat or pressure.
One AMU of mass is equal to 931 meV of energy (E = mc2).
Nuclear forces are strong and short ranged.


General

The most important formulas in the physics regents are:


Physics is fun. (Honest!)

test +1 and +2

WI$H TEST SERIES #PHYSICAL WORLD AND MEASUREMENT# M.M.20
1. Define Science and Physics . 2
2. Discuss scope of Physics. 2
3. What is the relation between Physics with Mathematics and Chemistry. 4
4. Define strong and weak nuclear forces. 4
5. State and prove Gravitation law and Coulomb’s law. 5
6. What do you mean by isolated system, law of conservation of charge and angular momentum? 3
vishaleasyphysics.blogspot.com




WI$H TEST SERIES # ELECTRIC FIELD # M.M.20
1. Define electric field, electric field intensity and write some properties of electric field lines. 4
2. Derive an expression for electric field intensity at any point on
(i) Axial line of dipole (ii) equatorial line of dipole (iii) at any point (iv) axis of uniformly charged ring. 3,3,3,3
3. A particle of mass m and change q is thrown at a speed u against a uniform electric field E. How much distance will it travel before coming to momentary rest? 4
vishaleasyphysics.blogspot.com

Speed and Velocity
Just as distance and displacement have distinctly different meanings (despite their similarities), so do speed and velocity. Speed is a scalar quantity that refers to "how fast an object is moving." Speed can be thought of as the rate at which an object covers distance. A fast-moving object has a high speed and covers a relatively large distance in a short amount of time. Contrast this to a slow-moving object that has a low speed; it covers a relatively small amount of distance in the same amount of time. An object with no movement at all has a zero speed.

Velocity is a vector quantity that refers to "the rate at which an object changes its position." Imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. While this might result in a frenzy of activity, it would result in a zero velocity. Because the person always returns to the original position, the motion would never result in a change in position. Since velocity is defined as the rate at which the position changes, this motion results in zero velocity. If a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. Every step must go into moving that person further from where he or she started. For certain, the person should never change directions and begin to return to the starting position.

Velocity is a vector quantity. As such, velocity is direction aware. When evaluating the velocity of an object, one must keep track of direction. It would not be enough to say that an object has a velocity of 55 mi/hr. One must include direction information in order to fully describe the velocity of the object. For instance, you must describe an object's velocity as being 55 mi/hr, east. This is one of the essential differences between speed and velocity. Speed is a scalar quantity and does not keep track of direction; velocity is a vector quantity and is direction aware.

The task of describing the direction of the velocity vector is easy. The direction of the velocity vector is simply the same as the direction that an object is moving. It would not matter whether the object is speeding up or slowing down. If an object is moving rightwards, then its velocity is described as being rightwards. If an object is moving downwards, then its velocity is described as being downwards. So an airplane moving towards the west with a speed of 300 mi/hr has a velocity of 300 mi/hr, west. Note that speed has no direction (it is a scalar) and the velocity at any instant is simply the speed value with a direction.

As an object moves, it often undergoes changes in speed. For example, during an average trip to school, there are many changes in speed. Rather than the speed-o-meter maintaining a steady reading, the needle constantly moves up and down to reflect the stopping and starting and the accelerating and decelerating. One instant, the car may be moving at 50 mi/hr and another instant, it might be stopped (i.e., 0 mi/hr). Yet during the trip to school the person might average 32 mi/hr. The average speed during an entire motion can be thought of as the average of all speedometer readings. If the speedometer readings could be collected at 1-second intervals (or 0.1-second intervals or ... ) and then averaged together, the average speed could be determined. Now that would be a lot of work. And fortunately, there is a shortcut. Read on.


Calculating Average Speed and Average Velocity
The average speed during the course of a motion is often computed using the following formula:


In contrast, the average velocity is often computed using this formula


Let's begin implementing our understanding of these formulas with the following problem:

Q: While on vacation, Lisa Carr traveled a total distance of 440 miles. Her trip took 8 hours. What was her average speed?
To compute her average speed, we simply divide the distance of travel by the time of travel.


That was easy! Lisa Carr averaged a speed of 55 miles per hour. She may not have been traveling at a constant speed of 55 mi/hr. She undoubtedly, was stopped at some instant in time (perhaps for a bathroom break or for lunch) and she probably was going 65 mi/hr at other instants in time. Yet, she averaged a speed of 55 miles per hour. The above formula represents a shortcut method of determining the average speed of an object.

Average Speed versus Instantaneous Speed
Since a moving object often changes its speed during its motion, it is common to distinguish between the average speed and the instantaneous speed. The distinction is as follows.

Instantaneous Speed - the speed at any given instant in time.
Average Speed - the average of all instantaneous speeds; found simply by a distance/time ratio.
You might think of the instantaneous speed as the speed that the speedometer reads at any given instant in time and the average speed as the average of all the speedometer readings during the course of the trip. Since the task of averaging speedometer readings would be quite complicated (and maybe even dangerous), the average speed is more commonly calculated as the distance/time ratio.

Moving objects don't always travel with erratic and changing speeds. Occasionally, an object will move at a steady rate with a constant speed. That is, the object will cover the same distance every regular interval of time. For instance, a cross-country runner might be running with a constant speed of 6 m/s in a straight line for several minutes. If her speed is constant, then the distance traveled every second is the same. The runner would cover a distance of 6 meters every second. If we could measure her position (distance from an arbitrary starting point) each second, then we would note that the position would be changing by 6 meters each second. This would be in stark contrast to an object that is changing its speed. An object with a changing speed would be moving a different distance each second. The data tables below depict objects with constant and changing speed.


Now let's consider the motion of that physics teacher again. The physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North. The entire motion lasted for 24 seconds. Determine the average speed and the average velocity.


The physics teacher walked a distance of 12 meters in 24 seconds; thus, her average speed was 0.50 m/s. However, since her displacement is 0 meters, her average velocity is 0 m/s. Remember that the displacement refers to the change in position and the velocity is based upon this position change. In this case of the teacher's motion, there is a position change of 0 meters and thus an average velocity of 0 m/s.

Here is another example similar to what was seen before in the discussion of distance and displacement. The diagram below shows the position of a cross-country skier at various times. At each of the indicated times, the skier turns around and reverses the direction of travel. In other words, the skier moves from A to B to C to D.

Use the diagram to determine the average speed and the average velocity of the skier during these three minutes. When finished, click the button to view the answer.



As a last example, consider a football coach pacing back and forth along the sidelines. The diagram below shows several of coach's positions at various times. At each marked position, the coach makes a "U-turn" and moves in the opposite direction. In other words, the coach moves from position A to B to C to D.

What is the coach's average speed and average velocity? When finished, click the button to view the answer.



In conclusion, speed and velocity are kinematic quantities that have distinctly different definitions. Speed, being a scalar quantity, is the rate at which an object covers distance. The average speed is the distance (a scalar quantity) per time ratio. Speed is ignorant of direction. On the other hand, velocity is a vector quantity; it is direction-aware. Velocity is the rate at which the position changes. The average velocity is the displacement or position change (a vector quantity) per time ratio.

Scalars and Vectors
Physics is a mathematical science. The underlying concepts and principles have a mathematical basis. Throughout the course of our study of physics, we will encounter a variety of concepts that have a mathematical basis associated with them. While our emphasis will often be upon the conceptual nature of physics, we will give considerable and persistent attention to its mathematical aspect.

The motion of objects can be described by words. Even a person without a background in physics has a collection of words that can be used to describe moving objects. Words and phrases such as going fast, stopped, slowing down, speeding up, and turning provide a sufficient vocabulary for describing the motion of objects. In physics, we use these words and many more. We will be expanding upon this vocabulary list with words such as distance, displacement, speed, velocity, and acceleration. As we will soon see, these words are associated with mathematical quantities that have strict definitions. The mathematical quantities that are used to describe the motion of objects can be divided into two categories. The quantity is either a vector or a scalar. These two categories can be distinguished from one another by their distinct definitions:

Scalars are quantities that are fully described by a magnitude (or numerical value) alone.
Vectors are quantities that are fully described by both a magnitude and a direction.
The remainder of this lesson will focus on several examples of vector and scalar quantities (distance, displacement, speed, velocity, and acceleration). As you proceed through the lesson, give careful attention to the vector and scalar nature of each quantity. As we proceed through other units at The Physics Classroom Tutorial and become introduced to new mathematical quantities, the discus

ntroduction to the Language of Kinematics
A typical physics course concerns itself with a variety of broad topics. One such topic is mechanics - the study of the motion of objects. The first six units of The Physics Classroom tutorial will involve an investigation into the physics of motion. As we focus on the language, principles, and laws that describe and explain the motion of objects, your efforts should center on internalizing the meaning of the information. Avoid memorizing the information; and avoid abstracting the information from the physical world that it describes and explains. Rather, contemplate the information, thinking about its meaning and its applications.

Kinematics is the science of describing the motion of objects using words, diagrams, numbers, graphs, and equations. Kinematics is a branch of mechanics. The goal of any study of kinematics is to develop sophisticated mental models that serve to describe (and ultimately, explain) the motion of real-world objects.

In this lesson, we will investigate the words used to describe the motion of objects. That is, we will focus on the language of kinematics. The hope is to gain a comfortable foundation with the language that is used throughout the study of mechanics. We will study such terms as scalars, vectors, distance, displacement, speed, velocity and acceleration. These words are used with regularity to describe the motion of objects. Your goal should be to become very familiar with their meaning.

Positive Affirmations
- I am healthy and happy.
- Wealth is pouring into my life.
- I am sailing on the river of wealth.
- I am getting wealthier each day.
- My body is healthy and functioning in a very good way.
- I have a lot of energy.
- I study and comprehend fast.
- My mind is calm.
- I am calm and relaxed in every situation.
- My thoughts are under my control.
- I radiate love and happiness.
- I am surrounded by love.
- I have the perfect job for me.
- I am living in the house of my dreams.
- I have good and loving relations with my wife/husband.
- I have a wonderful and satisfying job.
- I have the means to travel abroad, whenever I want to.
- I am successful in whatever I do.
- Everything is getting better every day.

"Sometimes love is for a moment, sometimes love is for a lifetime. "

"Sometimes a moment is a lifetime."
Once upon a time there was an island
where all the feelings lived together
One day there was a storm in the sea and the island was about to get drowned.


Every feeling was scared but Love made a boat to escape
Every feeling boarded the boat Only 1 feeling was left.

Love got down to see who it was...
It was EGO..

Love tried and tried but ego wasn't moving
Also the water was rising.
Every one asked love to leave him and come in the boat, but love was made to love. At last all the feelings escape and Love dies with ego on the island..

Love Dies because of EGO
So, Kill ego and Save Love

Give Your 100%

A boy and a girl were playing together. The boy had a collection of marbles. The girl had some sweets with her. The boy told the girl that he will give her all his marbles in exchange for her sweets. The girl agreed.

The boy kept the biggest and the most beautiful marble aside and gave the rest to the girl. The girl gave him all her sweets as she had promised.

That night, the girl slept peacefully. But the boy couldn't sleep as he kept wondering if the girl had hidden some sweets from him the way he had hidden his best marble.

Moral of the story: If you don't give your hundred percent in a relationship, you'll always keep doubting if the other person has given his/her hundred percent.. This is applicable for any relationship like love, friendship, employer-employee relationship etc., Give your hundred percent to everything you do and sleep peacefully .

VISHAL CHAUHAN( M.Sc. B.Ed.)


* WISH YOU ALL THE LUCK *

A careful analysis of the process of observation in atomic physics has shown that the subatomic particles have no meaning as isolated entities, but can only be understood as interconnections between the preparation of an experiment and the subsequent measurement.
Erwin Schrodinger

A universe with a God would look quite different from a universe without one. A physics, a biology where there is a God is bound to look different. So the most basic claims of religion are scientific. Religion is a scientific theory.
Richard Dawkins

Acceleration is finite, I think according to some laws of physics.
Terry Riley

PHYSICS TEST #ELECTRIC CHARGE AND COULOMB’S LAW# M.M. 20
1. State coulomb’s law and give its form in term of position vectors of charges. 3
2. Define superposition principle. 2
3. Give expression for electrostatics force due a uniformly charged line ,area and volume. 5
4. The nucleus of iron atom contains 26 protons.What repulsive electrostatic force acts between two protons in such a nucleus if they are 4*10^-15m apart? 5
5. Equal charges of 20 micro coulomb are placed at x= 0,2,4,8,16 cm on x-axis. Find the force experienced by the charge at x=2cm. 5
Vishaleasyphysics.blogspot.in



PHYSICS TEST #ELECTRIC CHARGE AND COULOMB’S LAW# M.M. 20
1. State coulomb’s law and give its form in term of position vectors of charges. 3
2. Define superposition principle. 2
3. Give expression for electrostatics force due a uniformly charged line ,area and volume. 5
4. The nucleus of iron atom contains 26 protons.What repulsive electrostatic force acts between two protons in such a nucleus if they are 4*10^-15m apart? 5
5. Equal charges of 20 micro coulomb are placed at x= 0,2,4,8,16 cm on x-axis. Find the force experienced by the charge at x=2cm. 5
Vishaleasyphysics.blogspot.in

WI$H PHYSICS TEST SERIES TEST-I #MATHEMATICAL TOOLS# M.M.20
1. Write binomial theorem. Evaluate (1001)^1/3 upto six places of decimal. 3
2. Find the logarithm of (i) 0.0568 (ii) 25.48 (iii) 786 (iv) 420 2
3. Differentiate w.r.t. x (i) x sin(nx) (ii) x^3/2 (iii)(5x^6+2x^1/2-x) 3
4. Find dot and cross product of A and B, A= 2i+j-k & B= -i-2j+k. 4
5. Evalute (i) sin 270 (ii) cot 315 (iii) tan135 (iv) sec 240. 4
6. Integrate w.r.t. x (i) x^n (ii) a^x (iii) e^x (v) sinx (v) cos x. 4
Vishaleasyphysics.blogspot.in

WI$H PHYSICS TEST SERIES TEST-I #MATHEMATICAL TOOLS# M.M.20
1. Write binomial theorem. Evaluate (1001)^1/3 upto six places of decimal. 3
2. Find the logarithm of (i) 0.0568 (ii) 25.48 (iii) 786 (iv) 420 2
3. Differentiate w.r.t. x (i) x sin(nx) (ii) x^3/2 (iii)(5x^6+2x^1/2-x) 3
4. Find dot and cross product of A and B, A= 2i+j-k & B= -i-2j+k. 4
5. Evalute (i) sin 270 (ii) cot 315 (iii) tan135 (iv) sec 240. 4
6. Integrate w.r.t. x (i) x^n (ii) a^x (iii) e^x (v) sinx (v) cos x. 4
Vishaleasyphysics.blogspot.in
WI$H PHYSICS TEST SERIES TEST-I #MATHEMATICAL TOOLS# M.M.20
1. Write binomial theorem. Evaluate (1001)^1/3 upto six places of decimal. 3
2. Find the logarithm of (i) 0.0568 (ii) 25.48 (iii) 786 (iv) 420 2
3. Differentiate w.r.t. x (i) x sin(nx) (ii) x^3/2 (iii)(5x^6+2x^1/2-x) 3
4. Find dot and cross product of A and B, A= 2i+j-k & B= -i-2j+k. 4
5. Evalute (i) sin 270 (ii) cot 315 (iii) tan135 (iv) sec 240. 4
6. Integrate w.r.t. x (i) x^n (ii) a^x (iii) e^x (v) sinx (v) cos x. 4
Vishaleasyphysics.blogspot.in

WI$H GUESS PHYSICS XI PAPER CONTACT@9855620961 M.M.65
SEMESTER-II
(i) Question No. 1 to 10 will be of 1 mark each.
(ii) Question No. 11 to 20 will be of 2 marks each.
(iii) Question No. 21 to 25 will be of 3 marks each.
(iv) Question No. 26 to 29 will be of 5 marks each & there will be 100%
internal choice.

1. When two bodies are said to be in thermal equilibrium?
2. Define radius of gyration.
3. What are the units of volumetric strain?
4. State Carnot’s theorem.
5. What is geostationary satellite?
6. Write law of equipartitian of energy.
7. What is damped oscillation.
8. What are units of viscosity?
9. Find out the centre of mass of a system of two bodies 20 cm apart. The masses of the bodies are 2 kg and 8 kg.
10. How far from the earth does acceleration due to gravity become one percent of its value at the earth’s surface ? Radius of earth = 6.38 ´ 10 6 m.
11. Tell why angular momentum is conserved with example?
12. Give example of reversible and irreversible processes.
13. Deduce relation between Cp and Cv.
14. State wain’s displacement and steafan’s law.
15. Give two applications of moment of inertia in daily life.
16. What is Pascal’s law? What are its applications?
17. Write a note on black body radiation.
18. Write the formulae for moment of inertia of Rod,Disc and Ring.
19. Define perpendicular and parallel axes theorems.
20. What is poision’s ratio?
21. In a simple harmonic motion, the velocities of a particle are 10 cm /s and 24 cm /s whenits displacements are 12 cm and 5 cm respectively. Calculate its periodic time andamplitude. [ October, 1998 ]( Ans: 3.14 sec, 13 cm )
22. A propagating harmonic wave expression is y = 0.05 sin ( 628t − 1.8x ) meter. Find thevalues of ( a ) the wave-length, ( b ) the frequency and ( c ) the velocity of the wave.[ April, 2002, October, 1990 ]( Ans: ( a ) 3.49 m, ( b ) 100 Hz, ( c ) 349 m / s )
23. State and prove equation of continuity.
24. Define Kepler’s laws.
25. Give two definitions of 2nd law of thermodynamics.
26. a) Derive formula for centre of mass of two particles system.
b) Prove linear momentum of centre of mass is conserved. Or a)Derive expression for orbital and escape velocity.b)Define terminal and critical velocity.
27. State and prove Bernoulli’s Theorem. Or a) Define Young’s, bulk and modulus of rigidity. b) What is elastic fatigue ? Give example.
28. Derive expression for time period of Simple pendulum. Or Derive expression for efficiency of Carnot’s engine.
29. What is capillary ? Derive Ascent’s formula. Or a)State and prove Newton’s law of cooling. b) State and prove Stoke’s law.

BEST OF LUCK FOR NEW SESSION