Question

A load of 220 kg is vertically pulled up by a crane through a vertical height of 16 m in 40 s. Calculate

1. Force acting in the upward direction
2. Total work done
3. Horse power of the engine pulling the rope.

[Take g = 9.8 ms⁻²; 1 HP = 750 W]

Answer 1

Given: Mass = 220 kg, height = 16 m, time = 40 s, and g = 9.8 ms⁻²

(a) The upward force needed to lift the load at constant speed equals its weight:

F = mg

= 220 × 9.8

= 2156 N

(b) Work done = force × height

= 2156 × 16

= 34496 J

(c) Power = `"work"/"time"`

= `34496/40`

= 862.4 W

Power in horsepower = `862.4/750`

≈ 1.15 HP