A mass on a spring oscillates vertically. Describe the changes in velocity and acceleration of the mass as it moves from the equilibrium position to the point of maximum displacement.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A mass is attached to a vertical spring and pulled down slightly from its rest position. When released, it oscillates up and down.
Model answer (5 marks)
At the equilibrium position the velocity of the mass is at its maximum. As the mass moves away from equilibrium towards the point of maximum displacement, its velocity decreases until it becomes zero at the extreme. The acceleration is directly proportional to the displacement from equilibrium and directed towards the equilibrium position; therefore it is zero at equilibrium and reaches its maximum magnitude at the point of maximum displacement.
Examiner tips
- Use the word "maximum" for velocity at equilibrium and "zero" at the extreme; mention that acceleration is proportional to displacement and directed towards equilibrium; keep the description concise and use correct terminology (velocity, acceleration, restoring force).
Common mistakes
- Confusing the points of maximum velocity and maximum displacement; writing that acceleration is zero at the extreme; omitting that acceleration is directed towards equilibrium.
Mark scheme (5 marks)
- At the equilibrium position the velocity of the mass is at its maximum
- As the mass moves away from equilibrium towards maximum displacement, velocity decreases
- At maximum displacement, velocity is zero
- Acceleration is directly proportional to displacement (from equilibrium) and directed towards the equilibrium position
- At maximum displacement, acceleration (and the restoring force) is at its maximum
Key terms in this question
equilibrium position · maximum displacement · velocity · acceleration
Related
- All AQA A-Level Physics (7408) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
More Periodic Motion questions
- A wine glass can shatter when exposed to a sound wave at a particular frequency.…
- A car suspension system uses springs and shock absorbers (dampers) to reduce the…
- A mass-spring system is set into oscillation. The system is then damped by attac…
- A tall building sways in the wind. Engineers design the building so that its nat…
- A buoy floating on the sea bobs up and down in simple harmonic motion. Explain w…
- A guitarist plucks a string on an electric guitar. The string vibrates and produ…