AQA GCSE Physics Physics Paper 2 (Foundation), June 2024: Question 9

14 marks · Standard Demand difficulty · Short Answer

Calculate forces, work done, and moments involving a child using a baby walker and associated toy gears.

Practise this question

Question

A multi-part physics question about a baby walker. Figure 17 shows a child using a baby walker, with sub-questions about resultant vertical force, work done, horizontal force, and motion from a carpet to a hard floor. Figure 18 shows two intermeshing toy gears, Gear A and Gear B, with a pivot, a radius of 7.5 cm, and a force of 2.0 N, followed by questions about moments and gear rotation.
Question text

09 Figure 17 shows a young child using a baby walker.

Figure 17

09.1 The child is standing still.

What is the resultant vertical force on the child?

Give a reason for your answer.

[2 marks]

Resultant vertical force = N

Reason

Use the Physics Equations Sheet to answer questions 09.2 and 09.3.

09.2 Write down the equation which links distance (s), force (F) and work done (W).

[1 mark]

09.3 The child pushed the baby walker 2.8 m across a horizontal floor.

The work done by the child was 35 J.

Calculate the horizontal force the child applied to the baby walker.

[3 marks]

Horizontal force = N

09.4 The child pushed the baby walker from a carpet onto a hard floor.

The child applied the same horizontal force to the baby walker.

Explain why the speed of the baby walker increased.

[2 marks]

There are some toy gears on the front of the baby walker.

Figure 18 shows the gears.

Figure 18

The child applies a force to gear A.

This causes a moment about the pivot, so gear A rotates.

Use the Physics Equations Sheet to answer questions 09.5 and 09.6.

09.5 Write down the equation which links distance (d), force (F) and

moment of a force (M).

[1 mark]

09.6 The child applies a force of 2.0 N on gear A.

The perpendicular distance between the force and the pivot is 7.5 cm.

Calculate the moment of the force about the pivot.

[3 marks]

Moment of force = Nm

09.7 Explain what happens to gear B when the child applies the force to gear A.

[2 marks]

Mark scheme

Show the mark scheme The official mark scheme for Question 9 detailing answers, extra information, marks, and AO spec references for parts 09.1 through 09.7.

Question 9

AO /

Question Answers Extra information Mark

Spec. Ref.

09.1 0 (N) 1 AO2

4.5.6.2.1

the child isn’t accelerating MP2 dependent on MP1 1

(vertically)

or

upwards forces are equal to the allow forces are balanced

downwards forces

AO /

Spec. Ref.

09.2 work done = force × distance 1 AO1

4.5.2

or

W = F × s

AO /

Spec. Ref.

09.3 35 = F × 2.8 1 AO2

4.5.2

35 1

F =

2.8

F = 12.5 (N) allow 13 (N) 1

AO /

Spec. Ref.

09.4 the resistive force has allow friction (between the 1 AO3

decreased wheels and the floor) has 4.5.1.4

decreased 4.5.6.2.1

4.5.6.2.2

so the resultant force increases 1

AO /

Spec. Ref.

09.5 moment = force × distance 1 AO1

4.5.4

or

M = F × d 21

AO /

Spec. Ref.

09.6 7.5 cm = 0.075 m 1 AO2

4.5.4

M = 2.0 × 0.075 allow a correct substitution of an 1

incorrectly / not converted value

of d

M = 0.15 (Nm) allow an answer consistent with 1

an incorrectly / not converted

value of d

AO /

Spec. Ref.

09.7 gear B rotates in the opposite 1 AO2

direction (to gear A) 4.5.4

or

gear B rotates clockwise

or

gear B rotates faster than gear

A

(because) gear A exerts a force 1

on gear B

or

(because) gear A causes a

moment about the pivot of gear

B

Total Question 9 14

How to answer it

Forces, Work Done and Moments Study Guide

What this question tests

This question assesses your understanding of resultant vertical forces, applying the work done equation, analyzing motion using resistive forces, recalling the moment of a force equation, performing unit conversions for calculations, and understanding how turning effects and gears operate.

Part 09.1: Resultant Vertical Force

Calculate and explain the vertical force on a stationary child

✅ Correct Answer

Resultant vertical force = 0 (N)

Reason: The child is not accelerating vertically (or upwards forces are equal to the downwards forces / forces are balanced).

Mark breakdown: 1 mark for 0 N, 1 mark for the correct reason. Note: MP2 is dependent on MP1.

💡 Key Knowledge

  • When an object is stationary or moving at a constant velocity, all the forces acting on it are balanced.
  • Balanced forces mean the resultant force is zero.

❌ Common Errors

Students often write random non-zero numbers or confuse vertical forces with the child's weight magnitude without linking it to the lack of vertical acceleration.

Part 09.2: Work Done Equation

Recall the equation linking distance, force, and work done

✅ Correct Answer

work done = force × distance
or
W = F × s

Mark breakdown: 1 mark for the correct equation or standard accepted symbols.

🧠 Exam Technique

Learn standard formula sheet equations word-for-word. Symbols like W , F , and s are acceptable as long as standard notations are used.

Part 09.3: Calculating Force from Work Done

Calculate the horizontal force applied by the child

📐 Step-by-Step Calculation

  1. State the equation: W = F × s
  2. Substitute known values: 35 = F × 2.8
  3. Rearrange to solve for F: F = 35 / 2.8
  4. Calculate final answer: F = 12.5 N (also accept 13 N if rounded appropriately)
Mark breakdown: 1 mark for substitution, 1 mark for rearrangement/calculation, 1 mark for final correct value (12.5 N).

❌ Common Errors

Multiplying work done by distance instead of dividing is a frequent calculator error. Always check if your calculated force makes logical sense in context.

Part 09.4: Explaining Changes in Speed

Explain why the walker's speed increased moving from carpet to hard floor

✅ Correct Answer

1. The resistive force (or friction between wheels and the floor) has decreased.
2. Therefore, the resultant force increases.

Mark breakdown: 1 mark for stating resistive force/friction decreased, 1 mark for linking it to an increase in resultant force.

💡 Key Knowledge

Carpet creates more friction against wheels than a smooth hard floor. Less friction means a smaller backward force, making the forward push yield a larger overall resultant force.

Part 09.5: Moment of a Force Equation

Recall the equation linking distance, force, and moment

✅ Correct Answer

moment = force × distance
or
M = F × d

Mark breakdown: 1 mark for the correct equation. Distance must be perpendicular distance in conceptual definitions.

Part 09.6: Calculating a Moment

Calculate the moment of the force about the pivot

📐 Step-by-Step Calculation

  1. Convert distance to meters: 7.5 cm = 0.075 m
  2. State the formula: M = F × d
  3. Substitute values: M = 2.0 × 0.075
  4. Calculate final value: M = 0.15 N m
Mark breakdown: 1 mark for unit conversion (7.5 cm to 0.075 m), 1 mark for correct substitution, 1 mark for final answer with correct unit (Nm).

❌ Common Errors

The Unit Trap: Forgetting to convert centimeters into meters ( 7.5 instead of 0.075 ). Examiners allow error-carried-forward if you consistently use 7.5 to get 15 , but converting units is essential for standard physics marks.

Part 09.7: Gears and Turning Effect

Explain what happens to gear B when force is applied to gear A

✅ Correct Answer

1. Gear B rotates in the opposite direction to gear A (or rotates clockwise / faster than gear A).
2. (Because) gear A exerts a force on gear B / gear A causes a moment about the pivot of gear B.

Mark breakdown: 1 mark for describing the correct motion/direction of gear B, 1 mark for explaining the transmission of force or moment.

💡 Key Knowledge

Interlocking gears always turn in opposite directions. A smaller gear paired with a larger gear (or vice versa) transmits turning forces directly through touching teeth.

Topics

Physics · P5: Forces

Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 2 (Foundation), June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.