A resting car starts accelerating uniformly at a1 rate a then moves at a constant velocity =4m/s then decelerates at a constant rate a2. the velocity of the car is greater than 2m/s for 10sec. What is the distance traversed by the car?

1 Answer
Jul 21, 2018

The total distance was 40m.

Explanation:

The car accelerates uniformly from rest to 4ms over some time t1. Then it decelerates uniformly for another time, t2. So the greatest speed was 4ms. We do not really know if the story continues until the car comes to a stop.We are asked to find total distance, but over how much of the story? Until the deceleration brings the car to a stop?

I will assume we need to find distance from start until the deceleration brings the car to a stop.

We are also told that the velocity was greater than 2ms for 10 s. It would have reached 2ms in a time of t12. And during the deceleration, it would have decreased to 2ms in a time of t22. Therefore

t12+t22=10sandt1+t2=20s

Because both a1anda2 are constant, and the peak velocity was 4ms, you can verify that the average velocity was 2ms using the formula

#v_"ave" = (u + v)/2

Therefore the total distance was

2ms(t1+t2)=2ms20s=40m

I hope this helps,
Steve