2. Gravitational Potential Energy

Learning outcomes
  • I can define gravitational potential energy as energy stored due to position in a gravitational field.
  • I can explain how mass, height, and gravitational field strength affect gravitational potential energy.
  • I can recall and use the equation ΔEp = mgΔh.
  • I can calculate changes in gravitational potential energy for objects raised or lowered vertically.
  • I can relate changes in gravitational potential energy to real-world systems such as roller coasters, dams, and falling objects.

Potential Energy

The amount of gravitational potential energy stored by an object at height can be calculated using the equation: 

Ep=mg h

where

  • Ep is measured in joules (J) 
  • m mass, is measured in kilograms (kg) 
  • g is gravitational field strength, measured in newtons per kilogram (N/kg) 
  • h is height,  measured in metres (m) 

Galileo takes a 5 kg cannonball to the top of the Tower of Pisa for one of his experiments. The tower is 56 m high. How much gravitational potential energy has the cannonball gained? (g = 10 N/kg) 

List:

  • h = 56m
  • g = 10 N/kg
  • m = 5 kg

Equation:

E = mgh

Solve:

E = 5(10)(56)

E = 2800 J

Potential Energy

Elastic potential energy is the energy stored in a spring, given by the equation:

EH=½m x2

Kinetic and Potential Energy Worksheet.pdf