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 upwards with an acceleration of $2m/s^2$, then the weight recorded in the machine will be

• A. $64$ kg
  
• B. $48$ kg
  
• C. $32$ kg
  
• D. $80$ kg
  

Answer 1

Answer: (B)

Mass of the man $m=40kg$

Acceleration of lift in upward direction $a=2m/s^2$

Let the weight shown by machine be $N$.

Equation of motion for the body : $ma=N-mg$

We get $N=m(a+g)$

$\therefore$ $N=\left(40\right)(2+10)=480$ N

Thus weight of the man recorded by machine $W^{\prime }=\frac{N}{g}$

$\therefore$ $W^{\prime }=\frac{480}{10}=48$ kg