# physics

posted by .

Olympic champion Justin gaitlin set a new world record for 100.0 m sprint at the last lympics by clocking 9.86 s for the race.Calculate
a)His average speed for the race
b)Assuming that he accelerated uniformly for the first 4.86 s after taking off the blocks to reach a maximum speed Vmax with which he continues for the rest of the race, is this speed likely to be same as, less than, or greater than the average speed.Why?
c)calculate the max. speed he reaches at the end of the first stage of his motion
d)Calculate the distance covered during the two stages and the steady acceleration in the first stage.

• physics -

Surely you can do (a) yourself.
For (b), consider if the average speed could ever exceed the maximum speed, and in what situation they could be the same.
For (c), the average speed during acceleration is Vmax/2 and the total distance travelled is
(Vmax/2)*4.86 s + Vmax*5.00 s. Set this equal to 100 m and solve for Vmax
I will be happy to critique your work on (d)