Question

In the figure shown, find the direction of friction on block A.

• A. $\text{Forward}$
• B. $\text{Backward}$
• C. $\text{Upward}$
• D. $\text{Downward}$

Answer 1

The correct option is B $\text{Backward}$


From the given system we can write,
$v_{AB}=2\hat{i}-(-3\hat{i})=5\hat{i}m/s^2.$
So, here $A$ appears to move to right. Hence, friction $\left(f_{AB}\right)$ will act backward on $A$ and in forward direction on $B$. (Since friction opposes relative motion)
The FBD of both the bodies are shown.



$f_{BA}$ represents friction acting on block B offered by block A.
$f_{BG}$ represents friction acting on block B offered by ground.