RECAP THE CONCEPTS

  • A force is a push or a pull.


  • A force can cause things to change its speed, direction, shape or size.

Gravitational force

  • Gravity is the force of attraction between objects.

  • Gravity depends on the mass of the objects and the distance between the objects.

  • Earth's gravitational force acts on all objects that are near it all the time, even when they are not moving.

Frictional force

  • Friction is a force that opposes motion.

  • Friction produces heat energy.

  • Friction can be useful (provides a grip to prevent slipping).

  • Friction can also be a problem as it causes moving parts to wear out or overheat.

Elastic spring force

  • Elastic spring force occurs when an elastic object is stretched, bent, twisted or compressed.

  • When a load is hung onto a spring, the spring stretches. Extension = New length - Original length.

  • The larger the load hanging on a spring, the greater the extension of the spring.

  • The load and extension are proportional up till a certain point.