Gravitational Potential Energy (CIE AS Physics)

What is Gravitational Potential Energy?

• Gravitational potential energy is energy stored in a mass due to its position in a gravitational field
  • Therefore energy is transferred to the object
  • When a heavy object is lifted, work is done since the object is provided with an upward force against the downward force of gravity

How can the equation for Gravitational Potential Energy be derived?

• This equation can therefore be derived from the work done

Derivation of GPE = mgh

• Gravitational potential energy (GPE) is energy stored in a mass due to its position in a gravitational field
  • If a mass is lifted up, it will gain GPE (converted from other forms of energy)
  • If a mass falls, it will lose GPE (and be converted to other forms of energy)

• The equation for gravitational potential energy for energy changes in a uniform gravitational field is:

Equation for GPE

GPE: The energy an object has when lifted up

• The potential energy on the Earth’s surface at ground level is taken to be equal to 0
• This equation is only relevant for energy changes in a uniform gravitational field (such as near the Earth’s surface)

GPE v Height graphs

• The two graphs below show how GPE changes with height for a ball being thrown up in the air and when falling down

Graphs showing the linear relationship between GPE and height

• Since the graphs are straight lines, GPE and height are said to have a linear relationship
• These graphs would be identical for GPE against time instead of height