A sprinter starts a 100 m race from rest and reaches a top speed before crossing the finish line. Describe the motion of the sprinter during the race, using the terms distance, speed, velocity and acceleration in your answer.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A sprinter competes in a 100 m race on a straight track. At the starting gun, the sprinter is stationary. The sprinter accelerates hard before maintaining a near-constant top speed for the remainder of the race.
Model answer (5 marks)
The sprinter starts from rest, so the initial distance is zero.
1. Distance – the sprinter covers 100 m in total; distance is a scalar and does not depend on direction.
2. Speed – during the race the sprinter’s speed is the rate of change of distance; it increases as the sprinter accelerates.
3. Velocity – velocity is the speed in a given direction; here it is a vector pointing along the straight track.
4. Acceleration – at the start the sprinter’s velocity increases, so the acceleration is positive.
5. After the initial acceleration phase the sprinter reaches a near‑constant top speed; acceleration becomes zero and velocity remains constant.
1. Distance – the sprinter covers 100 m in total; distance is a scalar and does not depend on direction.
2. Speed – during the race the sprinter’s speed is the rate of change of distance; it increases as the sprinter accelerates.
3. Velocity – velocity is the speed in a given direction; here it is a vector pointing along the straight track.
4. Acceleration – at the start the sprinter’s velocity increases, so the acceleration is positive.
5. After the initial acceleration phase the sprinter reaches a near‑constant top speed; acceleration becomes zero and velocity remains constant.
Examiner tips
- Use the exact terms (distance, speed, velocity, acceleration) as defined in the mark scheme.
- Show the relationship between acceleration and velocity (positive acceleration → speed increases).
- Mention that distance is scalar and velocity is vector.
- Keep the answer concise – 5 points, one sentence per point.
Common mistakes
- Confusing speed with velocity or omitting the direction aspect of velocity.
- Failing to state that acceleration is zero at top speed.
- Using vague phrases like “moving fast” instead of “speed”.
Mark scheme (5 marks)
- Distance is the total length of path travelled (accept: distance is a scalar quantity / distance does not depend on direction)
- Speed is the distance travelled per unit time (accept: rate of change of distance / how fast the sprinter is moving regardless of direction)
- Velocity is the speed in a given direction (accept: velocity is a vector quantity that has both magnitude and direction)
- At the start of the race the sprinter accelerates, meaning their velocity increases over time (accept: the sprinter's speed increases from zero / the rate of change of velocity is positive at the start)
- When the sprinter reaches top speed, acceleration is zero and velocity is constant (accept: at top speed the sprinter no longer accelerates / speed stays the same so acceleration = 0)
Key terms in this question
distance · speed · velocity · acceleration
Related
- All Eduqas A-Level Physics revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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