Question

It is friction that provides the force for a car to accelerate, so for high performance cars the factor that limits acceleration isn't the engine; it's the tires. For typical rubber-on-concrete friction, what is the shortest time in which a car coukd accelerate from 0 to 80 mph?

I used N=mg, μs=1.00, μr=0.02

m*ax=μs*N-μr*N

And then simplified to:

ax=(μs-μr)*g
ax=(1.00-0.02)(9.8 m/s2)= 9.604 m/s2
Then I used acceleration in this eq:
vf=vi+ax*t
80 mph= 0 mph + (9.604 m/s2)t
t= (80 mph/9.604 m/s2)(0.447 m/s / 1 mph)
t= 3.72 s

Please let me know if I approached this problem in the correct way and if my answer is right. Thank you.

Answer 1

Nah its 2.5 sec (to two sig figs)