Friction is a force that resists motion. It involves objects in contact with each other, and it can be useful or harmful. Friction helps when you want to slow or stop a bicycle, but it is harmful when it causes wear on the parts of a machine. In this activity, you will study the effects of surface smoothness and the nature of materials in contact on sliding friction. You will use the force sensor built into a Go Direct Sensor Cart to measure frictional force as you pull a block across different surfaces.


  • Measure friction between a wooden block and smooth-surface wood.
  • Measure friction between a wooden block and rough-surface wood.
  • Make predictions about other surfaces.
  • Test your predictions.