A) 0, 0
B) 0, 10 m/s
C) 10 m/s, 10 m/s
D) 10 m/s, 0
Correct Answer: B
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 = \[\frac{displacement}{time-\operatorname{int}erval}\] \[=\frac{0}{t}=0\] Average speed = \[\frac{\text{Distance}}{\text{Time-interval}}\] \[\text{=}\frac{\text{2}\pi r}{t}=\frac{2\times 3.14\times 100}{62.8}\] \[=\,10\,m/s\] 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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