Question

A block A of mass 2 kg rests on another block B of mass 8 kg which rests on a horizontal floor. The coefficient of friction between A and B is 0.2 while that between B and floor is 0.5. When a horizontal force 25 N is applied on the block B, the force of friction between A and B is:

• A. Zero
• B. $3.5$
• C. $5$
• D. $49$

Answer 1

The correct option is A Zero

The normal force acting on block $B$ is $N=(8+2)g=100N$

The frictional force $f=0.5N=50N$ , which is greater than applied force.

So the block $B$ does not move.

For block $A$, the acceleration is $2m/s^2$.

So the frictional for acting between $A$ and $B$ is $0$.

Therefore the cporrect option is $A$.