Question

A distressed car is rolling backward, downhill at 3.0 m/s when its driver finally manages to

get the engine started. What velocity will the car have 6.0 s later if it can accelerate at
3.0 m/s??

Answer 1

Step-by-step explanation:

Acceleration is equal to the change in velocity over the change in time, or

`a=(v_f-v_i)/(t)` where the change in velocity is final velocity minus initial velocity. Filling in:

`3.0=(v_f-(-3.0))/(6.0)` Note that I made the backward velocity negative so the forward velocity in our answer will be positive.

Simplifying that gives us:

`3.0=(v_f+3.0)/(6.0)` and then isolating the final velocity, our unknown:

3.0(6.0) = v + 3.0 and

3.0(6.0) - 3.0 = v and

18 - 3.0 = v so

15 m/s = v and because this answer is positive, that means that the car is no longer rolling backwards (which was negative) but is now moving forward.