Question

A car moves with speed 10m/s for time 20 minutes. Then 15 m/s for time 20 minutes and finally movewith speed 25 m/s for time 20 minutes, then the average speed

Answer 1

There are three parts, each with duration of 20 minutes:

Part 1: When speed = 10 m/s

Distance = speed × time

» D1 = 10 × 20 × 60

» D1 = 12000 m

Part 2: When speed = 15 m/s

Distance = speed × time

» D2 = 15 × 20 × 60

» D2 = 18000 m

Part 3: When speed = 25 m/s

Distance = speed × time

» D3 = 25 × 20 × 60

» D3 = 30000 m

Total distance = D1 + D2 + D3

» Total distance = 60000 m

Total time = 20 × 3 × 60

» Total time = 3600 s

Average Speed = Total distance/Total time

Average Speed = 16.67 m/s