Question

A speeding Thunderbird left skid marks on the road that were 76.7 m long when it came to a stop. If the acceleration of the car was -10 m/s2, how fast was the car initially going?

Answer 1

Answer: 39.2 m/s

Explanation:

You can use the kinematic equation:

$v_f^2=v_i^2+2a*d$

We know the final velocity because it says it came to a stop. So now all we gotta do is plug in.

$0^2=v_i^2+2(-10)(76.7)\\v_i^2=1,534\\v_i=\sqrt{1534} \\=39.166 m/s$