Question

A lift is moving up with an acceleration of $4m/s^2$. If $g=10m/s^2$. the weight of the man is:

• A. increased by $25\%$
• B. increased by $40\%$
• C. decreased by $20\%$
• D. decreased by $40\%$

Answer 1

The correct option is B increased by $40\%$

Suppose the mass of the man is $m$ then its weight in $rest$ frame will be $W_1=mg$

When he is in an elevator going $upward$ direction then he will feel a $downward$ $psuedo$ force and thus the weight $\left(downward\right)$

will increase and the new weight will be $W_2=mg+F_{psuedo}=mg+ma=m(g+a)=m(10+4)=14m$

so the $increment$ will be $\frac{W_2-W_1}{W_1}\times 100$ % $=\frac{14m-10m}{10m}\times 100$ % $=40$ %