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## A body travels 100m in first 2 seconds and 104 in the next 4 second.how far will it gimove in the next four second if the acceleration is uniform?

A body travels 100m in first 2 seconds and 104 in the next 4 second.how far will it move in the next four seconds if the acceleration is uniform?

## why in all the system of units time is always in second?

Please tell me why in all the system of units time is always in second? -Pankaj Sharma

## Do the super conductors obey the second law of thermodynamics?

Second law of thermodynamics is not violated.

If you can illustrate your idea and doubt, we may be able to discuss in more detail.

## Wave travelling from one medium to another

“when a wave enters from air to water, its wavelength changes but

frequency remains unchanged. why”

Velocity of a wave = frequency x time period

V = ν λ

When a wave travels from one medium to another, its velocity changes and so also is its wavelength, but frequency; which is the number of vibrations produced per second is independent of the medium, remains constant.

However, their is a phenomenon called Doppler Effect where the apparent frequency (observed frequency) is different from actual frequency and is caused by the relative movement between the source and observer (listener)

## Refraction through Prism – A Question

A light ray falls perpendicular to one of the faces of a glass prism of angle 60 and refractive index 1.5,
Find;
a) the angle of emergence.
b) the angle of deviation.
The ray will enter without any deviation. Therefore, the angle of incidence at the second face inside the prism = 60 degree
(From A +90+ (90-r2)=180)
Since the critical angle for glass is less than this, the ray of light will undergo total internal reflection. So it reflects towards the base internally.

## How OPERA found the fast µ neutrino traveled faster than light?

After the news of the neutrino travelling faster than light came, everyone is enquiring about this. Many students are of the opinion that “It is time to change the Physics Textbooks” But time has not come. It is just the first result pointing towards a possibility that some particles can travel faster than light. Here is an account of the result obtained by the researchers at OPERA.

Researchers on the Opera (Oscillation Project with Emulsion-tRacking Apparatus) experiment recorded the arrival times of ghostly subatomic particles called neutrinos sent from Cern on a 730km journey through the Earth to the Gran Sasso lab.

The trip would take a beam of light 2.4 milliseconds to complete, but after running the experiment for three years and timing the arrival of 15,000 neutrinos, the scientists discovered that the particles arrived at Gran Sasso sixty billionths of a second earlier, with an error margin of plus or minus 10 billionths of a second.

The measurement amounts to the neutrinos travelling faster than the speed of light by a fraction of 20 parts per million. Since the speed of light is 299,792,458 metres per second, the neutrinos were evidently travelling at 299,798,454 metres per second.

The result is so unlikely that even the research team is being cautious with its interpretation. Physicists said they would be sceptical of the finding until other laboratories confirmed the result.

Many think that IF neutrinos really traveled faster than light, the entire principles and theories proposed by Einstein would be proved wrong. But this is not true. One of the great dream of Einstein was the unification. This would pave way for the theory of unification of forces.

## Kinematics Numerical

1. A particle travels 20 m in 7th second and 24m in 9th sec. find initial velocity?
2. in a projectile motion , a body thrown from the ground ,at what angle both the vertical height and range will be equal?
3. The velocity v(cm/s) of a particle is given in terms of time t(in seconds) by the equation v = at+b/t+c. Dimension of a,b, and c are ?

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