Question

A car travels at 54km/h for first 20s, 36km/h for next 30s and finally 18km/h for next 10s. find its average speed​

Answer 1

Answer:

54 km/hr = 54 x 5/18 = 15 m/s

36 km/hr = 36 x 5/18 = 10 m/s

18 km/hr = 18 x 5/18 = 5 m/s

Case I

Speed = 15m/s

Time = 20 s

Distance = Speed x Time = 15 x 20 = 300 m

Case II

Speed = 10 m/s

Time = 30 sec

Distance = 10 x 30 = 300 m

Case III

Speed = 5 m/s

Time = 10s

Distance = 5 x 10 = 50 m

Total Distance = 300 + 300 + 50 = 650 m

Total time = 20 + 30 + 10 = 60 s

Average Speed

= (Total Distance travelled) / (total time taken)

= 650/60

= 65/6 m/s

=10.83 m/s

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Answer 2

Answer:

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