A force that exists between objects, even if they are not touching.

A force that exists between objects when they are touching.

The overall effect of a set of forces acting on an object is represented by a single resultant force.

A diagram showing all of the forces acting on a single object.

Forces come in equal and opposite pairs, which act on pairs of different objects.

Newton’s Third Law (with free body diagrams in 2D)

Combined science

In the Gravity in space unit, they will build on this knowledge to learn about centripetal forces, orbital motion, stellar evolution, red shift and the big bang.

In the Energy of moving objects unit, pupils learnt how to calculate the amount of energy of objects have because they are moving, stretched or in a gravitational field; and to calculate energy transfers using knowledge of energy conservation and dissipation.

Forces make things change

one force representing the overall effect of all forces on an object

a force that exists between objects only when they are touching

a force that exists between objects even if they are not touching

Match the following key terms to their definition.

A block rests on a table. Which of the following diagrams correctly shows the weight of the block?

A footballer kicks a football. Which of the following diagrams correctly shows the force of the boot on the football?

Newton’s Third Law explains that interactions can be described by a pair of forces, sometimes called a ‘third law pair’. Which of the following are characteristics of the forces in a third law pair?

A block rests on a table. Which of the following is the correct free body diagram for the block?

This is not a free body diagram of the ball.

The diagram shows a ball hanging from a spring without moving. Two forces are shown. Which of the following statements are correct?

Both have direction, but scalar quantities also have magnitude.

Both have magnitude, but scalar quantities also have direction.

Both have magnitude, but vector quantities also have direction.

Both have direction, but vector quantities also have magnitude.

What is the difference between scalar quantities and vector quantities?

Which of the following are vector quantities?

What is the meaning of the prefix ‘m’ in the units mm and mg?

What is the meaning of the prefix ‘k’ in the units km and kg?

What is the meaning of the prefix ‘M’ in the units MW and MJ?

Which of the following lengths are equal to 8.2 m?

This lesson will soon be taken down.

Newton’s Third Law (with free body diagrams in 2D)

Lesson outcome