Question

an object covers one third of a distance with a speed of 5 kilometre per hour and rest part with speed of 10 kilometre per hour find its average speed​

Answer 1

Average speed is the ratio of total distance travelled to total time taken.

So if X is the total distance travelled then we have given that X/3 distance covered with speed 5.5 m/s (20 km/h) and 2X/3 distance covered with speed 16.67 m/s (60km/s).

So time taken to cover X/3 distance= (X/3)/5.5=X/16.5 seconds.

And time taken to cover 2X/3 distance=

(2X/3)/16.67=2X/50.01 seconds.

So total time taken to cover distance X = (X/16.5)+(2X/50.01)=0.1X seconds.

And hence average speed= X/0.1X =10m/s =36km/h.

(Formula for time calculation:

Time=distance/speed)