Question

A man of mass $m$ is standing on weighing machine in an elevator accelerating upwards with an acceleration $a$. What will be the reading of weighing machine?

• A. $m(g-a)\text{N}$
• B. $m(g+a)\text{N}$
• C. $\frac{m}{(g-a)}\text{N}$
• D. $\frac{m}{(g+a)}\text{N}$

Answer 1

The correct option is B $m(g+a)\text{N}$


Free body diagram w.r.t. a observer from ground.
Using Newton's second law of motion,
$N-mg=ma$
So, $N=ma+mg=m(g+a)\text{N}$

As we know weighing machine measures normal reaction
So reading of machine will be
$m(g+a)\text{N}$