is the product of the mass and velocity of an object, p = m v, it is a vector quantity

is the velocity of an object at the start of a phase of motion, represented by u

is the velocity of an object at the end of a phase of motion, represented by v

is the change in momentum per second, this is equal to the resultant force acting on an object

Changing momentum

Physics

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

Resultant forces and their effects

Forces in two dimensions (including resolution of a force)

Moments, levers and gears

Balancing

Force, mass and acceleration (a = (v – u)/t)

Newton's Second Law (including inertia)

Stopping (and estimating stopping distances)

Conservation of momentum

Stopping safely

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.

This unit explores forces, interactions, and Newton’s laws, including motion, rotation, and momentum. It covers reaction times, stopping distances, and deceleration dangers. Emphasis is on force diagrams, calculations, experiments, and evaluating methods for accuracy and safety.

Forces make things change

the product of the mass and velocity of an object, $$p = m × v$$

the velocity of an object at the start of a phase of motion, $$u$$

the velocity of an object at the end of a phase of motion, $$v$$

the change in momentum per second, equal to the resultant force

Match the following key terms to their definition.

A bus of mass 4000 kg accelerates from 2.0 m/s to 4.5 m/s. Calculate the change in momentum of the bus.

A ball of mass 0.40 kg hits a wall at a velocity of 3.0 m/s. It bounces off in the opposite direction at 2.5 m/s.
Calculate the change in momentum for the ball.

Which of the following is equal to the rate of change of momentum of an object?

A pickup truck of mass 2000 kg is travelling at 12 m/s. It slows to 4 m/s in a time of 5 s.
Calculate the size of the force needed to do this.

A ball with mass 0.30 kg and speed 5.0 m/s hits a wall and bounces back, at the same speed, in the opposite direction. The impact lasts for 0.10 s.
Calculate the size of the force during the impact.

Which of the following is the product of the mass and velocity (mass × velocity) of an object?

Which of the following is the correct unit of momentum?

The momentum of an individual object in the system cannot increase.

The momentum of an individual object in the system cannot decrease.

The velocity of an individual object in the system cannot increase.

The velocity of an individual object in the system cannot decrease.

The total momentum of all objects in a closed system cannot change.

According to the principle of conservation of momentum, which of the following statements is correct?

a bus of mass 3000 kg travelling at 1 m/s

a skater of mass 60 kg travelling at 8 m/s

Starting with the greatest momentum, sort the following objects into order of decreasing momentum.

A bicycle and rider have a combined mass of 100 kg.
Calculate their acceleration when a resultant force of 250 N acts on them. 

A van of mass 2000 kg accelerates in a straight line from 5.0 m/s to 8.0 m/s.
Calculate the increase in momentum for the van. 
You do not need to give the unit.

Changing momentum

Lesson outcome