Question

Block A is kept on block B as shown in figure. It is known that acceleration of block A is $2m/s^2$ towards right and acceleration of block B is $3m/s^2$ towards right under the effect of unknown forces. Direction of friction force acting on A by B $({\mu }_{AB}=0.3)$

• A. is necessarily towards right
• B. may be towards right
• C. may be towards left
• D. may be zero

Answer 1

Answer: (B), (C), (D)

The correct options are
B may be towards right
C may be towards left
D may be zero

Since the forces are unknown, the direction of acting friction depends upon what the direction and magnitude of external forces acting on the bodies are. Thus, all directions and magnitudes are possible.