## If gravitation suddenly stops?!

If gravitation suddenly stops …… neglecting the rotation … if someone is standing on ground ….. will the normal reaction disappear?? If yes why? I want to know when does normal reaction acts on a body? and in the absence of weight why would it disappear?

(Ahwan Abhinandan Joshi asks)

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## A problem from Optics

A convergent beam of light passes through a diverging lens of focal length 0.2m and comes to focus at distance 0.3m behind the lens.Find the position of the point at which the beam would converge in the absence of lens?

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## What would happen if the Earth stopped rotating?

The speed of an object on earth’s surface near equator is approximately is 1670 kilometers/hour. So, if the earth stops rotating suddenly,  the objects on the surface of earth which are unbound will be thrown eastwards tangentially with the speed of rotation of earth.

## Kinetic Energy – Numerical Problem

a running man has half the kinetic energy that a boy of half his mass has.the man speed up by 1m/s and then has the same kinetic energy as the body. what were the original speeds of man and boy?

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## Spherical Mirror Problem

A rear view mirror used in a bus has a radius of curvature 3.5 m. If the driver of the bus locates a car at 10.0m behind the bus, find the position, nature and size of the image of the car.

Ans:

f = r/2=-1.75 m

u=-10m

v=?

$\LARGE \inline f=\frac{uv}{u+v}$

$\LARGE \inline v=\frac{uf}{u-f}$
$\LARGE \inline v=\frac{-10 \times -1.75}{-10-(-1.75))}=\frac{17.5}{8.25}=2.12m$

## Parallel Universe

Is there really a parallel universe?

As of now, the answer is not final. There are different ideas and explanation given on parallel universes. Some say if parallel universe are far away from us, whereas others say that they are very close to us.

String theorists say that there are actually 11 dimensions. They’d come to the conclusion that our Universe is just one bubble among an infinite number of membranous bubbles which ripple as they wobble through the eleventh dimension.

If we think on probability also, we cannot just be selfish to say that we are alone. There is an equal probability of many such universes with life too.

I feel the space is not sufficient to explain all these thing here. The following links will help you know further.

http://space.mit.edu/home/tegmark/multiverse.pdf

http://www.scientificamerican.com/article.cfm?id=parallel-universes

http://www.bbc.co.uk/science/horizon/2001/paralleluni.shtml

http://en.wikipedia.org/wiki/Parallel_universe_(fiction)