Question

Two bodies. X and Y of mass m and M respectively exert forces on each other and no other forces act on them. The force on X is F and the acceleration is a. Which of the following pairs is correct?

Magnitude of force on Y Magnitude of acceleration of Y
A. m/M x F a
B. F ma/M

Answer 1

Here,the force on the smaller block will be the reactional force exerted by the larger block on it and vice versa.

If,that force is `R` we can say,this force will act against the direction of applied force `F` on the smaller block.

Given,its acceleration is `a`

So,we can say, `F-R=ma...........................1`

For,the larger block,the reaction force by the smaller block is acting to cause its movements,but as there is no frictional force,it will also move,so we can write for it as,

`R=Ma'` (where, `a'` is the acceleration of the larger block)

Putting `R=Ma'` in `1` we get,

`F-Ma'=ma`

or, `a'=(F-ma)/M`

and, `R=F-ma` (from `1`)