PHysics help?

Question

THe acceleration of grav is 10m/s².
WHat is the greatest acceleration a runner can muster if the friction between her shoes and the pavement is 74% her weight?
Answer in m/s².

THANK YOU VERY MUCH

Answer 1

Let the runner's mass to be m. So his weight is mg and the friction force is 74%*mg. This is the maximum force (from earth) may push him forward without slippage:
f = ma = 74%*mg
Hence a = 74%*g = 7.4m/s^2