Question

Drag-race tires in contact with an asphalt surface have a very high coefficient of static fric.tion. Assuming a constant acceleration and no slipping of tires, estimate the coefficient of static friction needed for a drag racer to cover 2.1 km in 8 s, starting from rest.

Coefficient of static friction =

Answer 1

d = (1/2) a t^2
solve for a
F = m a = mu m g
so
mu = a/g

Answer 2

d=ut+1/2at² , u=0
2100=(0)t+1/2a(8)²
a=65.63m/s²

Fx=ma
Ffr=ma.{1}

Fy=ma , Fy= Fn-mg , Fy=0
Fn=mg.{2}

Ffr=µsFn
ma=µs(mg)
a/g=µs
65.63/9.8=µs
µs=6.70N