A driver goes to a shop and returns home in half an hour, and the odometer shows a total of 6 km travelled. What are the average speed and the average velocity?
AAverage speed 12 km/h and average velocity 12 km/h
BAverage speed 6 km/h and average velocity zero
CAverage speed zero and average velocity 12 km/h
DAverage speed 12 km/h and average velocity zero
Answer & Solution
Correct answer: D. Average speed 12 km/h and average velocity zero
1. Average speed is the distance travelled divided by the elapsed time.
2. Substitute the values: 6 km / 0.5 h = 12 km/h.
3. Average velocity is the displacement divided by the elapsed time.
4. A round trip finishes where it started, so the displacement is zero.
5. Zero divided by 0.5 h gives an average velocity of zero.
6. Quoting 6 km/h divides the distance by one hour rather than by half an hour.
_Source: OpenStax College Physics (CC BY 4.0), Ch 2 "Kinematics", section 2.3 Time, Velocity, and Speed_
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