# Grantham PHY220 Week 1 Assignment Problem 6

### A sports car moving at constant speed travels 150 m in 4.00 s. If it then brakes and comes to a stop while decelerating at a rate of 6.0 m/s2 , how long does it take to stop?

Solution:

The velocity before applying the brake is

$v=\frac{150\:m}{4.00\:s}=37.5\:m/s$

Solve for t until the velocity becomes zero

$v=v_0+at$

$t=\frac{v-v_0}{a}=\frac{0-37.5\:m/s}{-6.0\:m/s^2}=6.25\:s$