# physics

posted by .

John is driving at 25m/s. When he brakes, he accelerates at the rate of -5.0m/s^2.

How much time did it take him to stop?
How far does it take him to stop?

• physics -

v = Vi + a t
at end v = 0 so
0 = 25 - 5 t
t = 5 seconds

d = vi t + .5 a t^2
d = 25(5) - 2.5 (25)
d = 125 - 62.5
d = 62.5

## Similar Questions

1. ### Physics

You are driving to the grocery store at 20 m/s . You are 110m from an intersection when the traffic light turns red. Assume that your reaction time is 0.50s and that your car brakes with constant acceleration. _ How far are you from …
2. ### physics

The brakes are applied to a car traveling on a dry, level highway. A typical value for the magnitude of the car's acceleration is 4.75 m/s2. If the car's initial speed is 32.1 m/s, how long does it take to stop and how far does it …
3. ### physics

A car starts from rest and accelerates uniformaly at the rate of 0.98m/s in 1hr.what is its final velocity?
4. ### physics

Two cars are traveling along a straight-line in the same direction, the lead car at 25.0 m/s and the other car at 32.0 m/s. At the moment the cars are 40.0 m apart, the lead driver applies the brakes, causing his car to have an acceleration …
5. ### physics

Two cars are traveling along a straight-line in the same direction, the lead car at 25.0 m/s and the other car at 32.0 m/s. At the moment the cars are 40.0 m apart, the lead driver applies the brakes, causing his car to have an acceleration …
6. ### Physics

You are driving to the grocery store at 11.9m/s. You are 169.0m from an intersection when the traffic light turns red. Assume that your reaction time is 0.730s and that your car brakes with constant acceleration. How far are you from …
7. ### physics

A boy on a motor scooter is traveling at a velocity of 14.1 m/s when he applies his brakes in order to stop. How much time will it take him to stop if he slows down at a rate of 3.2 m/s2?
8. ### physics

You are driving to the grocery store at 20 m/s. You are 110 m from an intersection when the traffic light turns red. Assume that your reaction time is 0.70 s and that your car brakes with constant acceleration. How far are you from …
9. ### physics

You are driving your car along a country road at a speed of 21.5 m/s. As you come over the crest of a hill, you notice a farm tractor 35.7 m ahead of you on the road, moving in the same direction as you at a speed of 10.0 m/s. You …
10. ### physics

You are driving through town at 14 m/s when suddenly a car backs out of a driveway in front of you. You apply the brakes and begin decelerating at 3.3 m/s2.How much time does it take to stop?

More Similar Questions