Resource 4: Summary of forces for the teacher

Background information / subject knowledge for teacher

  • Forces are pushes and pulls.
  • A force has two characteristics: size and direction.
  • When forces act, they can change the shape of the things they act on. There is a bigger change from a bigger force.
  • We can use the change to provide a quantitative measure of forces.
  • Forces can be measured using a spring balance or force meter (newtonmeter) in units called newtons.
  • An object’s weight is the force of gravity acting on it, thus weight is a force.
  • The mass of an object is a measure of the amount of matter in it. It is constant and does not change.
  • All objects exert a force on each other: the size of the force depends upon their masses.
  • Gravity is the force that holds you down to the planet Earth.
  • The force of gravity is smaller on the moon than on Earth because there is less matter in the moon (smaller mass) than in the Earth.
  • On the Earth, every kilogram is pulled by gravity with a force of around 10 newtons towards the centre of the Earth.
  • There is a distinction between mass and weight. Mass is an intrinsic property of an object – no matter where you are, you always have the same mass. Your weight is the gravitational force that acts on you. Your weight acts downwards, towards the centre of the Earth.
  • Mass and weight have different units. Mass is measured in grams and kilograms, whereas weight (a force) is measured in newtons.
  • Friction is a force that resists movement.
  • A force is needed to start something moving, speed it up, slow it down or change its direction.
  • The bigger the force, the greater the acceleration (or deceleration) on a fixed mass.
  • When no overall force is acting on an object, it will remain stationary or continue at a steady speed in a straight line.

Adapted from: Developing Subject Knowledge – Jane Devereux

Resource 3: Force word spiders or burrs

Resource 5: How can we reduce friction?