What mistakes do students make with Physics on the move?

Uses an unrealistic mass such as 10 kg for a car. Choose a value of the order of 1000 kg. Forgets to convert a stopping time or speed into consistent units. Keep seconds and metres per second throughout. Gives an answer without a unit. State the force in newtons and round to a sensible number of significant figures.

What are the exam tips for Physics on the move in Physics OCR GCSE?

Write down the values you choose for mass and acceleration before substituting them into F = m × a. Show the substitution and the arithmetic so the estimate can be followed. Check the order of magnitude of your answer against everyday experience of road vehicles.

OCR · GCSE · Physics

Course version: J249 · Version from Sept 2018

Estimate the forces involved in typical situations on a public road…

Full specification wording

Physics on the move: estimate the forces involved in typical situations on a public road (content found only in the physics separate science qualification) (Higher tier only)

This statement applies only to the separate physics qualification and only at Higher tier.

Checked against the OCR J249 specification (opens in a new tab) on 29 October 2026.

Point 7 of 8

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

Selects realistic values for mass and for acceleration or deceleration in a road situation.
Applies F = m × a correctly to the chosen values.
Rounds the estimated force to a sensible number of significant figures and gives the unit in newtons.
Compares estimates and explains why a heavier vehicle or shorter stopping time gives a larger force.

Common mistakes and how to put them right

Uses an unrealistic mass such as 10 kg for a car.
Put it right: Choose a value of the order of 1000 kg.
Forgets to convert a stopping time or speed into consistent units.
Put it right: Keep seconds and metres per second throughout.
Gives an answer without a unit.
Put it right: State the force in newtons and round to a sensible number of significant figures.

Exam tips

Write down the values you choose for mass and acceleration before substituting them into F = m × a.
Show the substitution and the arithmetic so the estimate can be followed.
Check the order of magnitude of your answer against everyday experience of road vehicles.

Try the lesson

The start of the Physics on the move: estimate the forces involved in typical situations on a public road (content found only in the physics separate science qualification) (Higher tier only) lesson, made from checked teaching notes for this specification point.

Have a go first

A car of mass 1200 kg travelling on a public road brakes and decelerates at about 6 m/s². Estimate the braking force on the car.

Tip: press 1 to 4 to choose

Listen

This statement applies only to the separate physics qualification and only at Higher tier. Learners estimate the forces in everyday road situations by using F = m × a, choosing sensible values for mass and acceleration or deceleration. For a car of about 1000 kg braking from 20 m/s to rest in 4 s, the deceleration is 20 ÷ 4 = 5 m/s², so the force is about 1000 × 5 = 5000 N. Estimates should be rounded to one or two significant figures and stated with units. Learners should recognise that a heavier vehicle or a shorter stopping time gives a larger force, and should judge whether an answer is of a reasonable order of magnitude for a public road. A strong answer earns marks for these points. Selects realistic values for mass and for acceleration or deceleration in a road situation. Applies F = m × a correctly to the chosen values. Rounds the estimated force to a sensible number of significant figures and gives the unit in newtons. Compares estimates and explains why a heavier vehicle or shorter stopping time gives a larger force. Exam tip: Write down the values you choose for mass and acceleration before substituting them into F = m × a.

See it

A flowchart running top to bottom. The first box says choose realistic mass, of the order of 1000 kg, and points to a second box, choose acceleration or deceleration. That second box points to a third box, apply F = m × a, which points to a fourth box, round to one or two significant figures and give the force in newtons, which points to a fifth box, check the order of magnitude is reasonable for a public road. The second box also points to two further boxes: heavier vehicle gives a larger force, and shorter stopping time gives a larger force. — The steps for estimating a force on a vehicle using F = m × a, including the two factors that make the force larger.

Label the diagram

Some boxes have lost their names. Pick the right name for each number.

The diagram again, with 3 boxes numbered instead of named. A flowchart running top to bottom. The first box says choose realistic mass, of the order of 1000 kg, and points to a second box, choose acceleration or deceleration. That second box points to a third box, apply F = m × a, which points to a fourth box, round to one or two significant figures and give the force in newtons, which points to a fifth box, check the order of magnitude is reasonable for a public road. The second box also points to two further boxes: heavier vehicle gives a larger force, and shorter stopping time gives a larger force.

1Box 1
2Box 2
3Box 3

0 of 3 labelled

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