Question

A stone is released from the roof of an elevator going up with an acceleration of $5m/s^2$ . The acceleration of the stone with respect to lift is_____

• A. $5m{s}^{-2}$ downwards
• B. $4.8m{s}^{-2}$ upward
• C. $4.8m{s}^{-2}$ downwards
• D. $14.8m{s}^{-2}$ downwards

Answer 1

The correct option is D $14.8m{s}^{-2}$ downwards

We take positive sign for upward acceleration and negative sign for downwards acceleration.

Acceleration of elevator is $a_e$= 5 $m/s^2$ (upwards)

Acceleration of stone is $a_s$= - 9.8 $m/s^2$ (downwards)

Then acceleration of the stone with respect to lift ($a_{se}$) = $a_s$ - $a_e$=$-9.8-5=-14.8$

So acceleration of the stone with respect to lift is $14.8m/s^2$ downwards