Question

A man of mass $m$ stands on a weighing machine in a lift
$$\begin{array}{cc}\text{List-I}& \text{List-II}\\ \text{Lift moves}& \text{reading of machine}\\ \text{a) up with uniform acceleration '}a\text{'}& \text{e)}mg\\ \text{b) down with uniform acceleration '}a\text{'}& \text{f)}m(g+a)\\ \text{c) down with uniform velocity}& \text{g)}m(g-a)\\ \text{d) freely falling lift}& \text{h)}0\end{array}$$

• A. a - f ; b - g ; c - e ; d - h
• B. a - g ; b - f ; c - h ; d - e
• C. a - g ; b - e ; c - f ; d - h
• D. a - f ; b - g ; c - h ; d - e

Answer 1

The correct option is A a - f ; b - g ; c - e ; d - h

a) as lift is moving up with uniform acceleration, pseudo force acts down.
So $N=m(g+a)$
b) as lift is moving down with uniform acceleration,
pseudo force acts up
so, $N=m(g-a)$
c) Same as case 'b' but $a=0$
so $N=mg$
d) Same as case 'b' but $a=g$
$\Rightarrow N=m(g-a)$
$=0$