Question

A $60kg$ man is inside a lift which is moving up with an acceleration of $2.45{ms}^{-2}$. The apparent percentage change in his weight is,

• A. $20$
• B. $25$
• C. $50$
• D. $75$

Answer 1

Answer: (B)

$25$

Given,

$m=60kg$

$a=2.45m/s^2$

$g=10m/s^2$

Original weight, $W=mg$

$W=60\times 10=600N$

Apparent weight, $W^{\prime }=mg-ma$

$W^{\prime }=60(10-2.45)$

$W^{\prime }=453N$

The apparent percentage change in weight,

$\frac{W-W^{\prime }}{W}\times 100=\frac{600-453}{600}\times 100$

$=25$%

The correct option is B.