A smooth wedge A is secured inside a chamber suspended from a fixed...

When the cable holding the chamber is snapped, the chamber and the wedge fall freely under gravity with a downward acceleration $g$.

In the non-inertial reference frame of the freely falling wedge, a pseudo force of magnitude $mg$ acts upwards on the block $B$.

The effective acceleration due to gravity in the frame of the wedge is $g_{eff} = g - g = 0$.

Since the effective gravity is zero, the normal reaction between the block and the wedge becomes zero, and there is no force component along the incline to accelerate the block down the wedge.

As the block is placed with zero initial velocity relative to the wedge, it will experience no relative acceleration and will remain at rest with respect to the wedge.

Therefore, the block will stay at the top of the wedge.