Question

How much energy is gained by a box of mass $20kg$ when a man runs arrying the box with a speed of $3m{s}^{-1}$ to catch the bus? $(g=10m{s}^{-2})$

Answer 1

Given;
Mass of the box,$m=20kg$
Velocity, $v=3m{s}^{-1}$
When carrying the box at a speed 3 𝑚𝑠−1 , the work done by man appears as kinetic energy in the box.
Kinetic energy, $KE=\frac{1}{2}m{v}^2$
$=\frac{1}{2}\times 20\times 3^2=90J$
$\therefore \text{Energy gained by the box}=90J$