Question

A person standing on a spring balance inside a stationary lift measures $60kg$. The weight of that person if the lift descends with a uniform downward acceleration of $1.8m/s^2$ will be ___________ $N$. $[g=10m/s^2]$

Answer 1

Explanation for the correct answer:

Step 1. Given data:

Mass$M=60kg$

Acceleration $a=1.8\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s^2$}\right.$

Gravity on Earth $g=10m/s^2$

Since lift moves with downward acceleration, let the Normal Reaction $N$ is acting on upward direction.

Step 2. When lift moves with downward acceleration:

In frame of lift pseudo force will be in upward direction.

As we know that,

$$\begin{gathered} Ma=Mg–N \\ \Rightarrow N=M(g–a) \\ \Rightarrow N=60(10–1.8) \\ \Rightarrow N=60\times 8.2 \\ \Rightarrow N=492Newton \end{gathered}$$

Hence, the answer is $492N.$