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# Monthly Archives: April 2012

## What is gravity?

So I’ve been thinking about what gravity really is, I know it’s a rather weak force, but dominates the universe.  Is there a possibilities that gravity is actually inter-molecular forces? ## Direction of velocity and acceleration

Is it possible that the velocity and the acceleration of a body point in opposite directions? if yes then why?
if no then why?

Yes. It is possible for the direction of acceleration to be opposite to the direction of velocity.

Acceleration is the rate of change of velocity. If velocity is increasing while moving in a straight line then the direction of acceleration is same as the direction of velocity.

It the velocity is decreasing whil travelling in a straight line then the direction of acceleration is opposite to the direction of velocity.

Example: When a stone is thrown vertically upwardsm its acceleration is downwards and velocity is upwards. ## susceptibility

The susceptibility of annealed iron at saturation is 5500.find its permeability at saturation

Ans:                The absolute permeability, μ( = B/H) and the volume susceptibilityκ (= J/μ0H), are related by the equation: μ = μ0(1 + κ)

## CONDUCTING SLAB BETWEEN THE PLATES Schematic of a parallel plate capacitor with a dielectric spacer. Two plates with area A are separated by a distance d . When a charge pm{}Q is moved between the plates, an electric field E exists in the region between the plates. The dielectric material becomes polarised due to the charge displacement, reducing the total internal field, and increasing the capacitance. (Photo credit: Wikipedia)

How the value of capacitance change if we introduce conducting slab in between?

Sureshkumar kve

Capacitance increases as the distance between the plate reduces ## Change in resistance of a wire on stretching

A WIRE OF LENGTH L AND AREA OF CROSS SECTION A HAS A RESISTANCE R. IF THE WIRE IS STRACHED TO TWICE OF ITS LENGTH WHILE A REMAINS SAME , WHAT IS THE NEW RESISTANCE????

We know that R = ρl/A

When the wire is stretched, there is no change in volume. So if length is doubled then volume will be halved so that volume is constant.

Therefore, the new resistance R’ = 4R

That is the resistance becomes four times its original value.

1. A WIRE OF LENGTH L AND AREA OF CROSS SECTION A HAS A RESISTANCE R. IF THE WIRE IS STRACHED TO TWICE OF ITS LENGTH WHILE A REMAINS SAME , WHAT IS THE NEW RESISTANCE???? ## Why do we represent particle by a group of matter waves and not by single de Broglie wave

Why do we represent particle by a group of matter waves and not by single de Broglie wave? Two representations of a hydrogenic de-Broglie wave; the ring represents the electron's phase as a color, the wavy line shows the phase using a polar plot of a sinus curve. (Photo credit: Wikipedia) ## Problem from Kinematics

A particle moving with constant acceleration describes in the last second of its motion 9/25th of the total.if it starts from rest how long is the particle in motion and through what distance does it move if it describes 6 cm in first sec ### Hits so far @ AskPhysics

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