A car travels at 54 km/h for first 20 s, 36 km/h for next 30 s and finally 18 km/h for next 10 s. Find its average speed.
Step 1, Given data Speed = 54 km/hr = 54 x 518 = 15 m/s, Time = 20 sec Speed = 36 km/hr = 36 x 518 = 10 m/s, Time = 30 sec Speed = 18 km/hr = 18 x 518 = 5 m/s, Time = 10 sec Step 2: Formula used Average velocity = TotaldistanceTotaltime Step 3: Finding total distance 1st Case --- Speed = 15 m/s Time = 20 s Distance = Speed x Time = 15 x 20 = 300 m 2nd Case --- Speed = 10 m/s Time = 30 sec Distance = 10 x 30 = 300 m 3rd Case --- Speed = 5 m/s Time = 10 s Distance = 5 x 10 = 50 m Now Total Distance = 300 + 300 + 50 = 650 m Total time = 20 + 30 + 10 = 60 s Step 4: Finding average speed Average Speed =TotaldistanceTotaltime=65060=10.83 m/s Hence the average speed is 10.83 m/s.
