AQA A-Level Physics Paper 1, June 2022: Question 25

1 mark · Medium difficulty · Multiple Choice

Identify which force forms a Newton's third law pair with the weight of a parachutist descending at constant speed.

Practise this question

Question

Multiple choice question with an image of a parachutist descending with an open parachute. Below the image is the question asking which force makes a Newton's third law pair with the parachutist's weight, with four options: A (drag force on the parachutist), B (tension in the strings), C (gravitational force of the parachutist on the Earth), and D (lift force on the parachute).
Question text

25 A parachutist descends to the ground at a constant speed with the parachute open.

Which force, together with the parachutist’s weight, makes a pair according to Newton’s

third law of motion?

[1 mark]

A the drag force on the parachutist from the air

B the tension in the strings of the parachute

C the gravitational force of the parachutist on the Earth

D the lift force on the parachute from the air

Mark scheme

Show the mark scheme The mark scheme table shows question number 25 has the correct answer C (AO1), corresponding to the gravitational force of the parachutist on the Earth.

25 C (AO1) the gravitational force of the parachutist on the Earth

How to answer it

Newton's Third Law and Parachutists

What this question tests

This question assesses your precise understanding of Newton's Third Law of Motion. Specifically, it tests whether you can identify interacting force pairs, recognize the difference between Newton's third law pairs and balanced forces (Newton's first law), and apply the definition that a third law pair must act on two different bodies and be of the same physical type.

Question 25 [1 mark]

Identifying a Newton's Third Law Pair

✅ Correct Answer

C — the gravitational force of the parachutist on the Earth

💡 Key Knowledge

  • Newton's Third Law definition: When two bodies interact, the forces they exert on each other are equal in magnitude and opposite in direction.
  • Characteristics of a valid pair: Same type of force (e.g., gravitational), acting on two different objects, in opposite directions.
  • The weight of the parachutist is Earth's gravitational pull on the parachutist. Therefore, its Newton's third law counterpart must be the parachutist's gravitational pull on the Earth.

🧠 Exam Technique

Always use the standard template for Newton's third law wording when thinking through options: "Object A exerts force on Object B, therefore Object B exerts an equal and opposite force on Object A." If both forces act on the same object (like drag and weight acting on the parachutist), it's a Newton's First Law scenario (forces balancing for constant speed), not a third law pair!

❌ Common Errors

  • Option A (Drag): Students often incorrectly pair weight with drag or upthrust because the parachutist is falling at a constant speed. However, drag and weight act on the same object and are of different types (gravitational vs. frictional/fluid resistance).
  • Confusing First and Third Law: Mistaking balanced forces producing constant velocity (zero net force) for Newton's third law pairs.
Examiner Insight: This style of multiple-choice question frequently catches out candidates who confuse the conditions for equilibrium (Newton I) with interaction pairs (Newton III). Always check that the two forces involve swapped subject/object pairs (e.g., Earth-Parachutist and Parachutist-Earth).

Topics

Physics · 3.4 Mechanics and materials

Question and mark scheme from the AQA A-Level Physics examination, Paper 1, June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.