OCR A-Level Physics B H557
Planning
Implementing
Analysis
Evaluation
Practical Skills
Use of Apparatus and Techniques
Fundamental Data Analysis
Imaging and Signalling
Sensing
Mechanical Properties of Materials
Waves and Quantum Behaviour
Space, Time and Motion
Creating Models
Out Into Space
Our Place in the Universe
Matter: Very Simple
Matter: Hot or Cold
Electromagnetism
Charge and Field
Probing Deep Into Matter
Ionising Radiation and Risk
Creating Models
Simple harmonic motion: the defining relationship
- 2 things to know
- Components 01, 02 and 03
Overview
Recall questions on defining simple harmonic motion, a = −ω²x and its minus sign, the restoring force condition, the mass–spring equation of motion and ω = √(k/m), ω = 2πf, amplitude and period, calculating angular frequency, maximum acceleration and maximum speed, zero acceleration at equilibrium, and why the period is independent of amplitude.
What you need to know
Answer each one before you reveal it.
What does the minus sign in a = −ω²x mean physically?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define simple harmonic motion.
Model answer
It is oscillation in which the acceleration is proportional to the displacement from equilibrium and is always directed towards the equilibrium position.
- 2
What relationship links acceleration and displacement in simple harmonic motion?
Model answer
The acceleration is a = −ω²x, where ω is the angular frequency and x the displacement.
- 3
What does the minus sign in a = −ω²x mean physically?
Model answer
The acceleration is always opposite in direction to the displacement, so it points back towards equilibrium.
- 4
What condition must the restoring force satisfy for simple harmonic motion?
Model answer
It must be proportional to the displacement and directed towards the equilibrium position.
- 5
Write the equation of motion for a mass on a spring in terms of the spring stiffness.
Model answer
The motion obeys d²x/dt² = −(k/m)x.
- 6
How does the angular frequency of a mass–spring system depend on stiffness and mass?
Model answer
The angular frequency is ω = √(k/m).
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