Question

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?

• A. The average speed of the car in going from O to P and come back to Q is 20 m s^-1
• B. The average velocity of the car in going from O to P and come back to Q is 10 m s^-1
• C. The average speed of the car in going from O to P and come back to O is 20 m s^-1
• D. The average velocity of the car in going O to P and come back to O is 20 m s^-1

Answer 1

Answer: (D)

The average velocity of the car in going O to P and come back to O is 20 m s^-1

Answer 2

For O to P and come back to Q

Average speed $= \frac{Pathlength}{Time{int}erval} = \frac{OP + PQ}{\Delta t}$

$= \frac{(360 + 120)m}{24s} = 20ms^{- 1}$

Average velocity $= \frac{Displacement}{Time{int}erval}$

$= \frac{240m}{24s} = 10ms^{- 1}$

From O to P and come back to O

Average speed $= \frac{360m + 360m}{36s} = 20ms^{- 1}$

Average velocity $= \frac{0m}{36s} = zero$