Question

A weightlifter is lifting weights of mass 200 kg up to a height of 2 metres. If g = 9.8 m s⁻², calculate :
(a) potential energy acquired by the weights.
(b) work done by the weightlifter

Figure

Answer 1

(a) Mass of the weights, (m) = 200 kg
Acceleration due to gravity, (g) = 9.8 m/s²
Height above the ground, (h) = 2 m
We can calculate potential energy as,
F.E = m × g × h
So,
$$\begin{gathered} P.E=200\times 9.8\times 2\mathrm{J} \\ =\boxed{3920\mathrm{J}} \end{gathered}$$

(b) Potential energy of a body kept at some height is equal to the amount of work done against gravity in moving the body to that position. Therefore, work done by the weight lifter is $\boxed{3920\mathrm{J}}$.