GPE

When you lift up an object, you are doing work on it. The object gains gravitational potential energy (or GPE) as it is lifted. The GPE of an object is the energy it has because of its position in a gravitational field, like the one around the Earth.

On Earth the gravitational field strength is 10 N/kg. An object’s GPE depends on the mass of the object, its height above the ground and the strength of the gravitational field. To calculate any change in GPE we can use this equation: change in GPE = mass × gravitational field strength × change in height (joules, J) (kilograms, kg) (newtons per kilogram, N/kg) (metres, m) If Ep is the gravitational potential energy, m the mass, g the gravitational field strength and h the change in height, then Ep = m × g × h

During this air-sea rescue the winch pulls a man weighing 90 kg from the sea into the helicopter 12 m above. How much GPE has the man gained? g = 10 N/kg. Using: Ep = m × g × h Ep = 90 × 10 × 12 Ep = 10 800 J = 10.8 kJ