Friction

Question

Friction

anonymous · Answer

The friction coefficient between an athlete's shoes and the ground is 0.90. Suppose a superman wears these shoes and races for 50 m. There is no upper limit on his capacity  of running at high speeds.
a)Find the minimum time that he'll have to take in completing the 50m starting from rest.
b)Suppose he takes exactly this minimum time to cover 50m, what minimum time will he take to stop?

anonymous · Answer

I somehow get the right answers but i dont quite know how

anonymous · Answer

Plz correct me where im wrong

|dw:1339256371683:dw|
Friction=N(0.9)=mg(0.9)
Friction=ma
so i get acceleration 9m/s^2
does this mean that he will always accelerate at this rate ?