Question

A man is instructed to carry a package from the base camp at B to summit A of a hill at a height of 1200 metres. The man weighs 800 N and the package weighs 200 N. If g = 10 m/s²,

1. how much work does man do against gravity?
2. what is the potential energy of the package at A if its is assumed to be zero at B?

Answer 1

Weight of the man (W₁) = 800 N

Weight of the package (W₂) = 200 N

Height of hill (h) = 1200 m

Acceleration due to gravity (g) = 10 m/s² 

(1) So total weight,

W = W₁ + W₂

W = (800 + 200) N

W = 1000 N

Since we know that, weight w = m × g

Thus, w_t = m × g = 1000 N    

Height climbed from the base camp at B to summit A, h = 1200 m

Work done in lifting a body = Weight of body × Vertical distance

= 1000 × 1200 J 

= 1200000

= 12 × 10⁵ J

(2) We can calculate potential energy as

P. E = m × g × h

P. E = (200) (1200) J

= 240000 J

= 2.4 × 10⁵ J