AQA A Level Physics复习笔记4.6.5 Kinetic & Gravitational Potential Energy

Kinetic Energy

• Kinetic energy is the energy an object has due to its motion (or velocity)
  • The faster an object is moving, the greater its kinetic energy

   

• When an object is falling, it is gaining kinetic energy since it is gaining speed
  • This energy transferred from the gravitational potential energy it is losing

   

• An object will maintain this kinetic energy unless its speed changes

Kinetic energy (KE): The energy an object has when its moving

Gravitational Potential Energy

• 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:

Gravitational potential energy (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