Question

The elevator shown in the following figure is descending with an acceleration of 2 m/s². The mass of the block A is 0.5 kg. What force is exerted by the block A on the block B?

Answer 1

When the elevator is descending, a pseudo-force acts on it in the upward direction, as shown in the figure.  

From the free-body diagram of block A,
\[mg - N = ma\]
\[N = m\left( g - a \right)\]
\[ \Rightarrow N = 0 . 5\left( 10 - 2 \right) = 4 N\]
So, the force exerted by the block A on the block B is 4 N..