CIE A Level Physics复习笔记5.2.1 Gravitational Potential Energy

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

• 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