Calculate the power spent by a crane while lifting a load of mass 2000 kg, at velocity of 1.5 ms-1. (g = 10 ms-2).

Given: mass m = 2000 kg, velocity v = 1.5 m s⁻¹, g = 10 m s⁻²

To lift a load at a steady speed, the crane must apply a force equal to the weight: F = m g = 2000 × 10 = 20 000 N

Power = force × velocity = 20 000 × 1.5 = 30 000 W

Power spent by the crane = 30 000 W (30 kW)

P = F × v is the form to use when you are given a speed rather than a time — it saves you inventing a distance and a duration that then cancel.

The force is the WEIGHT, mg, not the mass. Using 2000 N instead of 20 000 N gives 3 000 W, out by a factor of ten. The question gives you g precisely so that you convert mass to weight.

Lifting at a steady speed means the upward force exactly balances the weight — there is no extra force needed for acceleration.