Question

A dog walks for 10 minutes 800 m toward the east direction along a deserted road. Looking for his dog, his owner drives a car, finds him and takes the dog back to his house, 1.8 Km to the west direction with an average speed of 10 m/s. What is the magnitude of the average velocity of the dog for its entire journey.

Answer 1

Average velocity is always (net displacement )/( total time taken)

So in going back, the time taken by the car = 1800/10= 180 second.

Now total time for dog traveling=( 10 minutes+ 180 second)=780 seconds.

Net displacement= 1800-800= 1000 meter

(As once it is moving towards east and then 2nd time it is moving towards west.)

So average velocity= 1000/780 =1.28 m/second

Or 4.61 km/ hr.

Note: keep in mind it is asked net velocity not average speed. Average speed will be different from this.