Physics Problem?

Question

In coming to a stop, a car leaves skid marks 92 m long on the highway. Assuming a deceleration of 7.00 m/s^2, estimate the speed of the car just before braking.

Walkthrough please; I need to know how to do these not just the answer.

Thanks guys.

Answer 1

vf^2 = vi^2 + 2a(d)

That's your formula. vf stands for final velocity, vi stands for initial velocity.

Plug in your numbers

0^2 = vi^2 + 2(-7.0)(92)

vi = 35.89 m/s

Answer 2

e=-7/2t^2+vot = 92
0=-7t+vo so t = vo/7
and
-7/2(vo^2/49) +vo^2/7=92
vo^2= 14*92 and vo= 35.89m/s