Question

The elevator shown in figure (5−E5) 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?

Figure

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,
$mg-N=ma$
$$\begin{gathered} N=m\left(g-a\right) \\ \Rightarrow N=0.5\left(10-2\right)=4\mathrm{N} \end{gathered}$$
So, the force exerted by the block A on the block B is 4 N.