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# Tag Archives: Ohm’s law

## Angle between acceleration and velocity in projectile motion

What is the angle between the directions of acceleration and velocity at the highest point of projectile?

Answer:

At the highest point of a projectile, the vertical component of velocity is zero and the velocity is entirely **horizontal.** The direction of acceleration (due to gravity) is vertically downwards throughout the motion of the projectile.

Therefore, **the angle between the direction of acceleration and velocity at the highest point of a projectile is 90 °**

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## Motion of connected system – A numerical problem

What is the acceleration of the body m2 in the diagram below?

(The question was posted by Shuvam Shukla. Students and other visitors can post solution as comments to this post)

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## V proportional to I or I proportional to V in Ohm’s Law?

Why we used I proportional to V?

Can we write V proportional to I also?

Answer:

Both are ok. If we are changing the current and observing the voltage, then it is V∝ I

If we are changing the voltage and observing the current, then

I∝ V

In general, we write

**the dependent variable proportional to the independent variable**

dependent variable = the quantity measured by us

independent variable = the quantity fixed by us

## 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????

Answer:

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????