AQA AS Level Physics Paper 2, November 2021: Question 11

1 mark · Medium difficulty · Multiple Choice

Identify the work done on an object of mass m accelerated from rest to velocity v by a constant resultant force F.

Practise this question

Question

Multiple-choice question 11 asks for the work done on an object of mass m accelerated from rest to a velocity v by a constant resultant force F. Four options are given: A (Fv / 2), B (Fv), C (mv^2), and D (mv^2 / 2), each with a corresponding selection box.
Question text

11 An object of mass m is accelerated from rest to a velocity v by a constant resultant force F.

What is the work done on the object during this acceleration?

[1 mark]

Fv

A

B Fv

C mv2

mv2

D

Mark scheme

Show the mark scheme The mark scheme table shows that question number 11 corresponds to the correct answer D, representing mv^2 / 2.

mv2

11 D

How to answer it

Work Done by a Constant Resultant Force

What this question tests

This question assesses your understanding of the relationship between work done, force, displacement, and kinetic energy (the Work-Energy Principle). It tests whether you can link linear mechanics definitions (Work = Force × distance) with kinematic equations of motion to derive energy relationships without relying on final formulas alone.

Question 1.1 [1 mark]

Determining Work Done During Acceleration

✅ Correct Answer: D

The correct option is D ( mv²/2 ).

Mark allocated: 1 / 1 for selecting option D.

💡 Key Knowledge

  • Work-Energy Principle: The work done on an object equals its change in kinetic energy ( ΔEₖ = ½mv² - ½mu² ). Since it starts from rest ( u = 0 ), Work Done = ½mv² .
  • Definition of Work: W = F × s (Force multiplied by displacement in the direction of the force).

🧠 Exam Technique

If you aren't immediately sure how F and v combine into an energy expression, substitute standard kinematic equations into W = Fs :

  • F = ma
  • s = ½at² or use v² = u² + 2as giving s = v² / (2a)
  • Substitute into work: W = m × a × (v² / 2a)
  • The acceleration a cancels out, leaving ½mv² .

❌ Common Errors

  • Choosing B (Fv): Many students incorrectly assume power or simple dimensional scaling applies, confusing power ( P = Fv ) with work done.
  • Forgetting the factor of ½: Confusing constant force displacement work with simple momentum or incorrect kinetic energy equations.

Topics

Physics · 3.4 Mechanics and materials

Question and mark scheme from the AQA AS Level Physics examination, Paper 2, November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.