Question

A helicopter lifts a $72$ $kg$ astronaut, $15$ $m$ vertically from the ocean by means of a cable. The acceleration of the astronaut is $g/10$. What is the velocity of astronaut? $(g=9.8m/s^2)$

• A. $54.2m{s}^{-1}$
• B. $5.42m{s}^{-1}$
• C. $6.42m{s}^{-1}$
• D. $542m{s}^{-1}$

Answer 1

The correct option is B $5.42m{s}^{-1}$

Net work done in moving an object under application of a number of forces=$F_{net}\Delta s$

$=ma\Delta s$

$=72\times \frac{9.8}{10}\times 15J=1058J$

This energy goes into the kinetic energy of the object.

$⟹\frac{1}{2}m{v}^2=1058J$

$⟹v=5.42m/s$