AQA A-Level Physics Paper 1, June 2023: Question 31
1 mark · Easy difficulty · Multiple Choice
Identify which quantity has its magnitude at a minimum value when a mass undergoing simple harmonic motion between points P and Q is at Q.
Practise this questionQuestion
Question text
31 A mass, attached to two springs, oscillates horizontally between P and Q. The motion of
the system is simple harmonic.
Which quantity has its magnitude at a minimum value when the mass is at Q?
[1 mark]
A the acceleration of the mass
B the kinetic energy of the mass
C the potential energy of the mass–spring system
D the resultant force of the springs on the mass
Mark scheme
Show the mark scheme
31 B the kinetic energy of the mass
How to answer it
Simple Harmonic Motion: Quantities at Extremes
This question assesses your understanding of the spatial variations of kinematic and energetic quantities during Simple Harmonic Motion (SHM). Specifically, it tests your ability to distinguish between quantities that reach their maximum magnitudes at the equilibrium position versus those that reach their maximum magnitudes (or minimum magnitudes) at the turning points (amplitude positions P and Q).
Question 3.1
Identifying Minimum Magnitude Quantities in SHM
✅ Correct Answer
B — the kinetic energy of the mass
At position Q (an amplitude/turning point), the mass momentarily comes to rest. Therefore, its velocity is zero, making its kinetic energy EK = 0.5 mv² at a minimum (zero).
💡 Key Knowledge
- At Amplitude (P & Q): Displacement ( x ), acceleration ( a ), resultant force ( F ), and potential energy ( EP ) are at their maximum magnitudes. Velocity and kinetic energy are at their minimum (zero).
- At Equilibrium (Center): Displacement, acceleration, force, and potential energy are zero (minimum magnitude). Velocity and kinetic energy are at their maximum magnitudes.
🧠 Exam Technique
Read the stem very carefully: check whether the question asks for a maximum or minimum, and whether it refers to magnitude or vector direction. Here, Q is a displacement extreme, meaning it is a turning point where speed hits zero.
❌ Common Errors
- Confusing kinetic energy with potential energy. Students often associate extremes of motion with maximums for all physical quantities.
- Assuming acceleration or force is zero at the extremes because the mass stops momentarily. Remember that acceleration is driven by displacement ( a = -ω²x ), so maximum displacement gives maximum acceleration!
Topics
Physics · 3.6 Further mechanics and thermal physics (A-level only)
Question and mark scheme from the AQA A-Level Physics examination, Paper 1, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.