Question

A woman drives 6 miles, accelerating uniformly from rest to 70 mph. How long does it take for her to reach 70 mph?

Answer 1

Using the two kinematic equations that can be used for this problem are:
Vf = Vi + at and d=Vit +(1/2)*at^2
Since Vi (initial velocity) = 0 

The equations can further be simplified where a is the acceleration, t is the time, Vf is the final velocity which is 70 miles per hour and d is 6 miles

Vf = at
70 = at
a = 70/t---equation 1

d=(1/2)*a*(t^2)
6 = (1/2)*a*(t^2) ---equation 2

Substituting equation 1 to equation 2.
6= (1/2)*(70/t)*(t^2)
6= 35t
t= 0.17142 hours or 10.28571 mins or 617.14 sec