Question

A body of mass 2 kg is hung on a spring balance mounted vertically in a lift. if the lift descend with an acceleration equal to the acceleration due to gravity 'g' the reading on the spring balance will be

• A. $2kg$
• B. $(4\times g)kg$
• C. $(2\times g)kg$
• D. zero

Answer 1

The correct option is D zero

Mass of the body$m=2kg$

Acceleration of lift in downward direction $a=g$

Let the reading of spring balance be$N$.

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

Or $mg=mg-N$ $(\because a=g)$

$⟹$ $N=mg-mg=0$

Thus the spring balance will show zero reading.