Question

A dog runs 120m away from his master in a straight line in 9.0 s, and then runs halfway back in one third time. calculate the average speed

Answer 1

here dog travels 120 m in 9s and 60m in 3s thus total distance covered = 180m
and total time taken = 12s
therefore av speed = 180/12= 15m/s

Hope this will help you

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Answer 2

Given:

A dog runs 120m away from his master in a straight line in 9.0 s.

To find:

Average speed of dog ?

Calculation:

• First of all, let's calculate the total distance :

Total distance = 120 + 120/2 = 120 + 60 = 180 m.

• Now, total time be T :

T = 9 + 9/3 = 9 + 3 = 12 seconds.

So, average speed is :

$\therefore \: avg. \: v = \dfrac{total \: distance}{total \: time}$

$\implies\: avg. \: v = \dfrac{180}{12}$

$\implies\: avg. \: v = 15 \: m {s}^{ - 1}$

So, average speed of dog is 15 m/s.