A car is moving along a straight line OP as shown in the figure. It moves from O to P in 18 s and returns from P to Q in 6 s. Which of the following statements is not correct regarding the motion of the car ?

Explanation

(i) Average velocity `=("Total displacement")/("Total time interval")`
`v_(av)=(+360)/(18s)=+20 ms^(-1)`
Average speed `=("Path length")/("Time interval")=(360m)/(18s)=20 ms^(-1)`
Thus, in this case, the average speed is equal to the magnitude of the average velocity.
(ii) In this case,
Average velocity `=("Total displacement")/("Total time")=(+240 m)/((18+6.0)s)`
`=+10 ms^(-1)`
Average speed `=("Path length")/("Time interval")=(OP+PQ)/(Delta t)`
`=((360+120)m)/(24 s)=20 ms^(-1)`