Push a toy car or roll a marble across a table and observe as it slows down and comes to rest. The car stops because there is a force acting on it. Friction is the force that opposes the movement of an object. There are several forces acting on the moving car:

  • The forward force from the push that was given to the car. This causes the wheels of the car to turn. The wheels then push on the surface of the table.
  • The force of friction between the tyres and the surface
  • Air resistance

Objects that move through the air experience the frictional force of the air, which acts in the opposite direction to their movement. Air resistance acts against gravity on falling objects. As the speed of the falling object increases, the air resistance increases.