The difference between speed and velocity
3 marks · NormalA car slows down from 18 m/s to 6 m/s in 4 seconds. Calculate its acceleration.
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-3.0 m/s^2 (±0.1)
Also accept: –3; –3.0
Common mistakes: Not using negative sign
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Marking points
M1 · 1 mark · Correctly uses a = (v-u)/t formula.
A1 · 1 mark · Substitutes values correctly: v = 6, u = 18.
A2 · 1 mark · Gives correct answer: –3.0 m/s^2 with negative sign and unit.
Worked solution