Question

How do i find the average speed for his question: "A bicycle racer rides from a starting marker at 10m/s. She then rides back along the same rout from the turnaround marker at 16m/s. What is her average speed for the whole race?",

Answer 1

Average speed = Total Distance/Total time ------(1) Let us assume that the distance from starting marker to turnaround marker is 'x' Total distance travelled = 2x Speed from starting marker to turnaround marker , s1 = 10 m/s Speed from turnaround market to starting market , s2 - 16 m/s Let, Time taken from starting marker to turnaround marker be t1 Time taken from turnaround marker to starting marker be t2. Applying these values in equation (1), Average speed = (2x)/(t1+t2) -------(2) From (1), t1 = x/s1 = x/10 t2 = x/s2 = x/16 Substituting the above in (2), Average speed = (2x)/(x/10+x/16) m/s = (2x)/(13x/80) m/s = 160/13 m/s = 12.3 m/s We can also arrive at the average speed by using the formula 2(s1)(s2)/(s1+s2)

Answer 2

To find the average speed for the whole race, you just have to add the speed from a starting marker and the speed from the turnaround marker going back and divide it by 2 since there are only two speeds involved.

10 m/s + 16m/s = 26 m/s / 2 = 13 m/s

Therefore, the average speed for the whole race is 13 m/s.