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
Space, Time and Motion
Describing motion: displacement, velocity and acceleration
- 3 things to know
- Components 01, 02 and 03
Overview
Recall questions on average and instantaneous velocity, average speed against average velocity, (u + v)/2 and why it needs constant acceleration, uniform acceleration and its unit, cyclist and train calculations, negative acceleration, zero velocity with non-zero acceleration, choosing a positive direction, and finding instantaneous velocity from readings.
What you need to know
Answer each one before you reveal it.
Define instantaneous velocity.
How does average speed differ from average velocity for a journey that is not in a straight line?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define average velocity.
Model answer
Average velocity is the total displacement divided by the total time taken.
- 2
Define instantaneous velocity.
Model answer
Instantaneous velocity is the rate of change of displacement at a particular moment, the value approached as the time interval is made vanishingly small.
- 3
How does average speed differ from average velocity for a journey that is not in a straight line?
Model answer
Average speed uses the whole distance travelled, so it is greater than the magnitude of the average velocity, which uses only the displacement.
- 4
Give the average velocity of a body that accelerates uniformly from u to v.
Model answer
The average velocity is (u + v)/2.
- 5
Why does the relationship average velocity = (u + v)/2 hold only for constant acceleration?
Model answer
Only if the velocity changes at a steady rate is the mean of the initial and final values equal to the true average over time.
- 6
A cyclist speeds up uniformly from 4.0 m s⁻¹ to 10.0 m s⁻¹ in 12 s. Calculate the acceleration.
Model answer
The acceleration is (10.0 − 4.0)/12 = 0.50 m s⁻².
Other ways to work this
The same content, four other ways.
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Six ways to work the same material.
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