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# Tag Archives: doubt

## 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.

## Superman, Time Travel, Relativity and confusion!

In the original Superman movie, Superman flies around the world opposite its rotation at a speed faster than light (or close o it) and witnesses time running backwards. But at such speed, time would slow down for Superman, but not stop, and certainly not move backwards, would it? Instead of seeing people and events moving backwards and undoing themselves, wouldn’t everything on Earth appear to simply stop moving to Superman?

It was a common belief among the fans of relativity that – ” if any object travelled with the speed of light, then time would stop for him and if he traveled faster, he would go back in time.”

But, there is some tweaks required somewhere which we strongly expect to take place in the near future which would remove the absurdity in theory and practice.

Superman” is fiction and was considered a person who can go back in time. This was not based on relativity. But, based on the results of relativity, we tried to believe that such a thing is possible if we could travel that fast.

When Superman goes back in time, He going to that past and correcting some mistakes happened in the past. Such a thing is practically impossible with the present technologies  and techniques.

## IIT Kanpur : Previous Question Papers of JAM for MSc

Previous years Question Papers of JAM

 Paper Name 2005 2006 2007 2008 BT BT BT BT BT CA CA CA CA CA CH CH CH CH CY GG GG GG GG GG GP GP GP GP GP MA MA MA MA MA MS MS MS MS MS PH PH PH PH PH

## Kinematics Numerical Problems

The velocity m, v m/s, of a particle is a straight line is given by
v = 6+pt+qt³
where t is the time in seconds after the particle passes through a fixed point O.
Given that t=2 s the distance of the particle from O is 16 m and its acceleration is 32m/s², calculate

a) the value of p and of q
b) the velocity of the particle at the instant when did acceleration is zero

## Numerical Problems from Pressure, Density and Floatation

1. Ramesh buys 6 bottles of syrup each containing 1litre. Each empty bottle weighs 400g. The density of syrup is 1.2 g/cm3. What weight does Ramesh have to carry home?

2. The volume of 900g of a substance is 1000 cm3. Will the substance sink or float in water if the density of water is 1g/cm3. What will be the mass of water displaced by the substance?

## Particle theory of light and refraction

According to particle theory of light if a light ray bends toward the normal while entering from medium 1 to medium 2 then how the velocity of light in medium 2 is greater than the velocity of light in medium 1 ?

When a medium enters a denser medium from a rarer medium, it bends towards the normal. This is the observation we have in hand and this phenomenon is called refraction.

Sir Isaac Newton tried to explain the phenomenon of refraction using his particle theory. He said that the particles of the denser medium attracts the particles with stronger force towards it which makes it bend towards the normal.

If there is such a force of attraction, then the speed of light would increase inside a denser medium. When the velocity of light in different media was determined by Foucault and other scientists, it was found that the velocity of light in denser medium is less than that in a rarer medium. So, Newton’s explanation of refraction was proved wrong.

## Power Factor

“A COIL  HAS  A POWER  FACTOR OF 0.707 AT 60Hz, THEN ITS  POWER  FACTOR AT 180Hz WILL BE- ……….?

Ans:

(to be posted soon)

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