Question

A man is standing on a weighing machine placed in a lift. When stationary, his weight is recorded as $40kg$. If the lift is accelerated upward with an acceleration of $2m/s^2$, then the weight recorded in the machine will be $g=10m/s^2$.

• A. $48kg$
• B. $32kg$
• C. $42kg$
• D. $40kg$

Answer 1

The correct option is A $48kg$

Weight of man $W=mg=40gN$ , $g=10m/s^2$
Lift is accelerated upwards with acceleration $a=2m/s^2$
The weight recorded will be given by the reaction on the floor, R.
$R-mg=ma$,
$R=m(g+a)$ =$40\times 12=480N=48kg$