Brief Description:

Students will build cars and use them to explore the concepts of potential and kinetic energy.

Grades: K-5

Time: 1 hour

Keywords: wheel and axle, simple machines, potential energy, kinetic energy, inclined planes

Lesson Objectives

  • Students will understand the difference between potential and kinetic energy
  • Students will learn about wheels and axles


  • Legos or Lego simple machines kits
  • Ramp
  • Ramp Cars worksheet (see resources)


  1. Introduce the wheel and axle. Because this is the most well-known simple machine, this activity is also used to explore the concepts of kinetic and potential energy using a car as the example.
  2. Tell student that they design challenge is to build a car that will travel down a ramp and then travel the farthest horizontal distance from the bottom of the ramp.
    1. Tell students about potential energy. The energy that the car has at the top of the ramp before it is released (stored energy). This energy is converted into kinetic energy (the energy of the movement of the car has while moving).
      1. Explain that potential energy is highest at the top of the ramp (explain this by telling students that the car has the ‘potential’ to travel the farthest when it is placed here vs. when it is placed lower on the ramp). Potential energy is affected by gravity and the mass of the car.
      2. Explain that the kinetic energy is highest when the car is just at the bottom of the ramp because this is when it is moving the fastest, but has no more potential energy from being on the ramp.
      3. Explain that the force of friction – the force of the ground on the tires – is what slows the car down when it reaches the bottom of the ramp. Without friction, the car would continue to go forever in the same direction at the same speed.
    2. Tell students that they can build their car however they would like using the material provided. They can change the number of wheels, type of wheels, axles, etc. Remind them to think about potential energy, kinetic energy, and the forces of friction
  3. Have students build and test their cars. Allow each group three tests and record the farthest trial on the board or on a sheet.
  4. Have the students fill out the ‘Ramp Car’ Worksheet.
  5. Bring the class together to discuss the activity.
    1. Talk about what would be different if the ramp was shallower, steeper, rougher, or smoother. Do a demonstration if possible. Use this demo to introduce (or remind students about) inclined planes.
    2. Discuss the different designs. Whose car went the farthest? What was different about this design? What did some of the other designs look like and why did they not go as far?
    3. Conclude by asking students how they might improve their designs

Extensions and Modifications:

  • Build a vehicle with less or more than four wheels


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