Question

A truck decelerates at a rate of 2 m/s2. If it starts with a velocity of 15 m/s, how long will it take to stop?

Answer 1

Use the formula Vf = Vo + at

Stop => Vf = 0

=> 0 = Vo + at => Vo = -at => t =-  Vo / a

Vo = 15 m/s

a = - 2 m/s^2

=> t = - 15 m/s / ( - 2 m/s^2) = 7.5 s

And you can find the distance travled by using the equation: d = Vo*t + at^2 / 2

=> d = 15 m/s * 7.5 s - 2m/s^2 * (7.5s)^2 / 2 = 56.25 m

Answer: 7.5s (and 56.25m)