Question

23. A car travels a certain distance with a speed
of 40 ms-1 and returns with a speed u. If the average speed for the whole journey is 48 ms-1, what is the value of u?
(Ans. 60 ms-l)​

Answer 1

Explanation:

time taken to travel a certain distance x with speed of 40 m/s =>x/40 seconds

time taken to return to initial point with speed u m/s =>x/u. Total time taken =>

x/40 +x/u and total distance =>2x.

Average speed => Total distance/total time taken => 2x/(x/40 +x/u) = 48 =>

2x/((40+u)x/40u)= 48 => 80u/(40+u) = 48 =>

80u = 1920+48u =>32u= 1920 =>u=1920/32 => u = 60m/s. Hope it helps you.