AQA A-Level Physics Paper 1, June 2024: Question 23

1 mark · Medium difficulty · Multiple Choice

Calculate the reading on weighing scales for a man of mass 75.0 kg standing in a lift accelerating upwards at 2.60 m s^-2.

Practise this question

Question

Multiple choice question 23 asks for the reading on weighing scales when a man of mass 75.0 kg stands in a lift accelerating upwards at 2.60 m s^-2. Four options are given: A 195 N, B 541 N, C 736 N, and D 931 N.
Question text

23 A man has a mass of 75.0 kg.

He stands on weighing scales in a lift that accelerates upwards at 2.60 m s−2.

What is the reading on the scales during the acceleration?

[1 mark]

A 195 N

B 541 N

C 736 N

D 931 N

Mark scheme

Show the mark scheme Mark scheme for question 23 indicating the correct answer is D, with a value of 931 N.

23 D 931 N AO2

How to answer it

Apparent Weight in an Accelerating Lift

What this question tests

This question assesses your understanding of Newton's second law of motion (F = ma), gravitational field strength, and how the normal contact force (the reading on a weighing scale) differs from true weight when an object experiences vertical acceleration.

Question 2.3

A-Level Physics Multiple Choice Question

✅ Correct Answer: D (931 N)

The correct option is D. The scale measures the normal contact force exerted on the man, which increases when accelerating upwards.

💡 Key Knowledge

  • Weighing scales measure the normal contact force (R), not mass.
  • When accelerating upwards, the resultant force is directed upwards: R - mg = ma .
  • Rearranging gives the scale reading: R = m(g + a) .

🧠 Exam Technique

For multiple-choice questions involving forces in lifts, sketch a quick free-body diagram on your working paper. Identify all vertical forces and establish the direction of acceleration to get the signs correct before plugging in numbers.

❌ Common Errors

  • Option C (736 N): Forgetting to account for acceleration and simply calculating mg = 75.0 × 9.81 .
  • Option A or B: Subtracting acceleration instead of adding it ( m(g - a) ), which corresponds to moving downwards with upward deceleration or accelerating downwards.

📐 Step-by-Step Calculation

  1. Identify given values: Mass ( m ) = 75.0 kg , Acceleration ( a ) = 2.60 m s⁻² , Gravitational field strength ( g ) = 9.81 m s⁻² (standard AQA value).
  2. Set up Newton's second law equation:
    R - mg = ma
  3. Rearrange to solve for R (the scale reading):
    R = m(g + a)
  4. Substitute the values:
    R = 75.0 × (9.81 + 2.60)
  5. Calculate the result:
    R = 75.0 × 12.41 = 930.75 N
  6. Round to appropriate significant figures:
    Given data ( 75.0 kg , 2.60 m s⁻² ) are given to 3 significant figures, yielding 931 N .
Mark allocation: [1 mark] awarded for selecting option D. AO2 (Application of knowledge).

Topics

Physics · 3.4 Mechanics and materials

Question and mark scheme from the AQA A-Level Physics examination, Paper 1, June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.