Question

When block is placed on a wedge as shown in figure, the block starts sliding down and the wedge also starts sliding on ground. All surfaces are rough. The centre of mass of (wedge + block) system will move

• A. leftward and downward
• B. rightward and downward
• C. leftward and upwards
• D. only downward

Answer 1

The correct option is B rightward and downward

From the FBD of wedge,


Due to the horizontal component $\left(N_x\right)$ of normal reaction $\left(N\right)$ wedge will accelerate along left direction.
$\Rightarrow$ To oppose relative motion, $f$ will act rightawards.
F.B.D for system of (wedge + block), let mass of block and wedge be $m,M$.


Due to external force ${}^{\prime }{f}^{\prime }$ along rightwards.
C.O.M of system move towards right.

Wedge is not displaced along vertical direction, however due to motion of block along down the wedge.
$\Rightarrow$ C.O.M of (wedge + block) will move downwards.

Hence, option $\left(b\right)$