Question

A man of mass m pulls a block with mass M with a rope. The block moves towards the right direction as shown in the figure below:

The magnitude of friction is the same between the man and the ground and between the block and the ground. If T is the tension on the rope, f is the frictional force acting on the block, which of the following expression correctly depicts the force experienced by the block ?

• A. $T-f=M\times a_B$
• B. $T-f=\frac{M}{a_B}$
• C. $T+f=M\times a_B$
• D. $\frac{T}{f}=M\times a_B$

Answer 1

The correct option is B

$T-f=\frac{M}{a_B}$

Assume the acceleration of the block to be $a_B$. Tension on the block is acting towards the right.
We know friction opposes motion so f is towards the left. In order for the block to move tension must be greater than f. The force experienced by the block which is
$M\times a_B$ will be equal to $T-f=M\times a_B$