AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), 2019: Question 3

9 marks · Standard Demand difficulty · Short Answer

Identify scalar quantities, distinguish vectors from scalars, state factors affecting momentum, and explain why two bumper cars stop after colliding using conservation of momentum.

Practise this question

Question

The question page contains four linked physics parts labelled 03.1 to 03.4. Part 03.1 asks which quantities are scalars and gives five tick-box options: displacement, distance, force, speed and velocity; part 03.2 asks for the difference between a vector quantity and a scalar quantity; part 03.3 shows a diagram of two bumper cars moving towards each other with arrows labelled momentum pointing in opposite directions and asks for two factors affecting the momentum of each car; part 03.4 asks students to explain why both bumper cars stop after the crash. The page includes answer lines and mark allocations of 2, 1, 2 and 4 marks respectively, total 9 marks.
Question text

03 Some quantities are scalars and some are vectors.

03.1 Which of the following quantities are scalars?

[2 marks]

Tick ( ) two boxes.

Displacement

Distance

Force

Speed

Velocity

03.2 Give the difference between a vector quantity and a scalar quantity.

[1 mark]

Bumper cars are a fairground ride and are designed to bump into each other.

Figure 5 shows two bumper cars moving towards each other.

The momentum of each bumper car is shown by an arrow.

Figure 5

03.3 Give two factors that affect the momentum of each bumper car.

[2 marks]

*09* 2

03.4 The bumper cars crash into each other and stop.

Explain why both bumper cars stop after the crash.

[4 marks]

Mark scheme

Show the mark scheme The mark scheme is a table with rows for questions 03.1 to 03.4, listing acceptable answers, extra guidance and marks. It states that the scalar quantities are distance and speed; a vector has direction whereas a scalar does not; factors affecting momentum include mass, velocity, friction or power of the motor; and the collision explanation must refer to zero total momentum after the collision, equal and opposite momenta before the collision, and conservation of momentum, or alternatively equal and opposite forces acting for equal times causing opposite accelerations. The total available marks shown are 9.

AO /

Question Answers Extra information Mark ID

Spec. Ref.

03.1 distance 1 AO1 A

6.5.4.1.3

speed 1

03.2 (both have magnitude) only a allow scalar does not have a 1 AO1 E

vector has direction direction 6.5.1.1

03.3 any two from: 2 AO1 E

6.5.5.2

• mass allow weight

• velocity allow speed or direction

• friction allow air resistance or drag

• power of the motor

03.4 total momentum is zero after the 1 AO3 E

collision (because the bumper cars 5.5.5.2

are stationary)

because the momentum of each 1

car before the collision was equal

(in magnitude) and opposite (in

direction)

so the total momentum of the 1

bumper cars was zero before the

collision

and momentum is conserved 1

OR

total momentum is zero after the

collision (because the bumper cars

are stationary) (1)

because the momentum of each

car before the collision was equal

(in magnitude) and opposite (in

direction) (1)

both cars exert an equal and

opposite force on each other 11

(for equal periods of time ) (1)

so the cars accelerate (in opposite

directions) (1)

Total 9

How to answer it

Scalars, vectors and momentum in bumper cars

What this question tests
You need to know the difference between scalars and vectors, choose the correct scalar quantities from a list, and explain momentum in a collision. It also tests whether you can use the diagram to identify that the two cars have equal and opposite momentum before the crash, and that total momentum is conserved.

Overall idea

💡 Key knowledge

  • Scalar = has size only.
  • Vector = has size and direction.
  • Momentum = mass × velocity.
  • Momentum is a vector, so direction matters.
  • In a closed system, total momentum is conserved.

🧠 Exam technique

  • For “tick two boxes”, choose exactly two answers.
  • For definitions, use short, clear wording.
  • For explanations, link your points logically: before collision → after collision → conservation.
  • Use “equal and opposite” when the diagram shows opposite directions.

Part 03.1 — Which quantities are scalars? [2 marks]

Tick two boxes.

✅ Correct answers

Distance

Speed

1 mark each for the two correct boxes.

💡 Key knowledge

  • Distance is scalar because it has magnitude only.
  • Speed is scalar because it has magnitude only.
  • Displacement, force and velocity are vectors because they have direction.

❌ Common errors

  • Ticking displacement because it sounds like distance.
  • Ticking force or velocity because they are “about movement”.
  • Choosing more than two boxes, which loses marks.

Part 03.2 — Difference between a vector and a scalar [1 mark]

✅ Correct answer

A vector has magnitude and direction, but a scalar has magnitude only.

🧠 Exam technique

  • Say both parts clearly for full credit.
  • AQA also accepts: “a scalar does not have a direction”.
  • Keep it short and precise.

❌ Common errors

  • Saying only “a vector is bigger than a scalar” — this is not correct.
  • Using vague words like “one is speed and one is force” instead of defining them.

Part 03.3 — Two factors that affect momentum [2 marks]

✅ Correct answers

Any two of:

  • mass
  • velocity
  • friction
  • power of the motor

Marking note: AQA also allows weight for mass, and speed or direction for velocity.

💡 Key knowledge

Momentum is calculated using:

momentum = mass × velocity

So the momentum of each bumper car depends mainly on:

  • the mass of the car
  • the velocity of the car

🧠 Exam technique

  • Choose two distinct factors.
  • If you write speed, it is accepted because speed affects velocity size.
  • If you write direction, it is accepted because momentum is a vector.
  • For this question, simple recall is enough — no calculation needed.

❌ Common errors

  • Writing “force” — force changes momentum, but it is not one of the listed accepted factors.
  • Giving only one factor.
  • Repeating the same idea twice, e.g. “speed” and “velocity”.

Part 03.4 — Explain why both bumper cars stop after the crash [4 marks]

✅ Full-mark answer

Before the collision, the two cars have equal momentum in size but opposite directions, so the total momentum is zero. After the collision, both cars are stationary, so the total momentum is still zero. Since momentum is conserved, this is why they stop after the crash.

💡 Key knowledge

  • The arrows in the diagram show the momenta are in opposite directions.
  • If the arrows are the same size, the momenta are equal in magnitude.
  • Stationary objects have zero momentum.
  • In a collision, total momentum before = total momentum after.

🧠 Exam technique

  • To score all 4 marks, make 4 linked points.
  • Use cause-and-effect language: “because”, “so”, “therefore”.
  • Refer to the diagram: equal size arrows, opposite directions.
  • You can earn full marks by either:
    • explaining zero total momentum before and after, or
    • explaining equal and opposite forces causing opposite acceleration after impact.

❌ Common errors

  • Saying “they stop because the force is used up” — not scientific enough.
  • Not mentioning that the momenta are equal and opposite.
  • Forgetting to state that stationary cars have zero momentum.
  • Confusing momentum with force.

📐 Step-by-step reasoning you could write in the exam

  1. The two cars move towards each other with momenta in opposite directions.
  2. The momenta are equal in size, so they cancel out.
  3. This means the total momentum before the collision is zero.
  4. After the collision the cars are stationary, so the total momentum is zero.
  5. Momentum is conserved, so the total momentum stays zero.
  6. Therefore both cars stop after the crash.

❌ Calculation-style traps, even though this is not a maths question

  • Forgetting that momentum is a vector.
  • Writing “the momenta add up” without checking directions.
  • Ignoring the fact that stationary = zero velocity = zero momentum.
  • Not linking the answer to conservation of momentum.

Quick revision summary

Scalar quantities in this question

Distance and speed

Vector quantities in this question

Displacement, force and velocity

Momentum idea

momentum = mass × velocity

Equal and opposite momentum can give a total of zero.

Topics

Physics · P5: Forces

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 2 (Higher), 2019. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.