# The friction coefficient between an athelete's shoes

Question:

The friction coefficient between an athelete's shoes and the ground is $0.90$. Suppose a superman wears these shoes and races for $50 \mathrm{~m}$. There is no upper limit on his capacity of running at high speeds.

(a) Find the minimum time that he will have to take in completingthe $50 \mathrm{~m}$ starting from rest.

(b) Suppose he takes exactly this minimum time to complete the $50 \mathrm{~m}$, what minimum time will he take to stop?

Solution: