Question

When Maggie applies the brakes of her car, the car slows down uniformly from 15.0 m/s to
0.0 m/s in 18.8 m. How long does it take the car to stop?

Answer 1

Explanation:

Given that,

Initial velocity, u = 15 m/s

Final velocity, v = 0

Time, t = 18.8 m

Let a is the acceleration of the car.

$v^2-u^2=2as\\\\a=\dfrac{v^2-u^2}{2s}\\\\a=\dfrac{(0)^2-(15)^2}{2\times 18.8}\\\\a=-5.98\ m/s^2$

Now using second equation of motion:

$18.8=15t+\dfrac{1}{2}\times (-5.98)t^2\\\\t=2.574\ s,2.443\ s$

Hence, the time is 2.574 s and 2.443 s