Question

The elevator shown in figure is descending with an acceleration of $2{\text{ms}}^{-2}$. The mass of the block $A=0.5\text{kg}$. The force exerted by the block $A$ on the block $B$ is $(g=10{\text{ms}}^{-2})$

• A. $2N$
• B. $4N$
• C. $6N$
• D. $8N$

Answer 1

The correct option is B $4N$

Drawing FBD of ${}^{\prime }{A}^{\prime }$


Here psuedo force acts upwards as lift is moving downwards with acceleration. $a=2{\text{ms}}^{-2}$
$\Rightarrow N+ma=mg$
$N=0.5(10-2)=4N$