Question

A car moves at a constant speed of 60 km/hr for 2 km and 40 km/hr for next 2 km.What is the average speed of the car?

Answer 1

Solution :


For first 1 km
Speed is 60 km / hr = 60/3600 km / sec
= ( 1 / 60 ) km / sec
= 0.01666 km / sec
We know that,
V = distance / time
Therefore,
Time = distance / velocity
Time = 1 / 0.01666 = 60 sec
Therefore car takes 60 seconds to cover first one km

For next 1 km
For first 1 km
Speed is 40 km / hr = 40/3600 km / sec
= ( 1 / 90 ) km / sec
= 0.01111 km / sec
We know that,
V = distance / time
Therefore,
Time = distance / velocity
Time = 1 / 0.1111 = 90 sec
Therefore car takes 900 seconds to cover another one km.
Total distance cover by car is 2 km in time ( 60 + 90 = ) 150 sec.
The Average speed is
Va = ( Total distance travel ) / (Time)
Va = 2 / 150
Va = 0.01333 km / sec
Va = 0.01333 X 3600 km / hr
Va = 48 km / hr

Therefore the average speed of car is 48 km / hr