Question

In the figure shown, a cubical block is held stationary against a rough wall by applying force $F$ then incorrect statement among the following is

• A. frictional force $f=Mg$
• B. $F=N,N$ is Normal reaction
• C. $F$ does not apply any torque
• D. $N$ does not apply any torque

Answer 1

Answer: (D)

$N$ does not apply any torque

The block will remain stationary against the wall
1. if the friction force is equal to the weight of the block, i.e $f=Mg$
2. If normal reaction, $N$ balance by the applied force F. i.e, $N=F$
3. As $F$ is applied on the block at a point so it will not create torque.
4. The normal reaction $N$ acts on every point on the block against the wall.
So the torque due to N is $=Nx$. Thus (D) is incorrect.