A) 0, 0
B) 0, 10 m/s
C) 10 m/s, 10 m/s
D) 10 m/s, 0
Correct Answer: D
Solution :
| Key Idea: In completing a circular lap, car's displacement is zero. |
| Average velocity is defined as the ratio of displacement to time taken while the average speed of a particle in a given interval of time is defined as the ratio of distance travelled to the time taken. |
| On a circular path in completing one turn, the distance travelled is \[2\pi r\] while displacement is zero. |
| Hence, average velocity \[=\frac{\text{displacement}}{\text{time-interval}}\] |
| \[=\frac{0}{t}=0\] |
| Average speed \[=\frac{\text{Distance}}{\text{Time-interval}}\] |
| \[=\frac{2\pi r}{t}=\frac{2\times 3.14\times 100}{62.8}\] |
| \[=\,10\,m/s\] |
| Note: If a particle moves in a straight line without change in direction, the magnitude of displacement is equal to the distance travelled to otherwise it is always less than it. |
| Thus, |displacement| \[\le \] distance |
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