Examples

• What is the kinetic energy of a 100 kg human running at 8 m/s?

  
  

  1Remember the equation for kinetic energy stored

  Ek = ½mv2

  2Substitute the values in

  Ek = ½ 100 × 82

  3Calculate the kinetic energy with correct units

  Ek = 3,200 J
• What is the change in gravitational potential energy for a diver of mass 60 kg who walks up from ground level to the 10 m platform?

  
  

  1Remember the equation for gravitational potential energy stored

  Ep = mgΔh

  2Substitute the values in

  Ep = 60 × 10 × 10

  3Calculate the change in gravitational potential energy with correct units

  Ep = 6,000 J
• Calculate the elastic potential energy of a spring that has been extended 100 cm, given that the spring constant is 8 N/m.

  
  

  1Remember the equation for elastic potential energy stored

  Ee = ½ke2

  2Substitute the values in

  Ee = ½ × 8 × 1²

  3Calculate the change in elastic potential energy with correct units

  Ee = 4 J