# Work, Force, and Brakes: Solving the Physics Problem

• laurenbaboran
In summary, the brakes of a 1452 kg car exert a force of 7.12 x 103 N to bring the car to a stop from a speed of 17.2 m/s in a distance of 100 m. This results in a total work done of 7.12 x 105 J. If the speed of the car were doubled, it would cover a distance of 400 m while stopping with the same average braking force. If the car originally stops in 6.2 s (100 m), the power developed by the brakes is 23.4 kW.

## Homework Statement

Use this information to answer the next 4 questions: The brakes of a 1452 kg car bring it to a stop from a speed of 17.2 m/s in a distance of 100 m.

## Homework Equations

15. How much work do the brakes do?
2.15 x 105 J
1.42 x 106 J
2.50 x 106 J
7.12 x 105 J

16. What average force do the brakes apply?
2.50 x 104 N
7.12 x 103 N
2.15 x 103 N
1.42 x 104 N

17. How much distance would the car cover as it stops if the speed were doubled? Assume that the average braking force remains constant.
400 m
100 m
200 m
800 m

18. If the car originally stops in 6.2 s (100 m), what power is developed by the brakes?
23.4 kW
2.15 kW
34.7 kW
230 kW

## The Attempt at a Solution

I am so lost and I don't even know where to start with these. If you can help me I will be so grateful!

hi laurenbaboran!

what is the definition of work done?

what theorems do you know about work done?​

one of those two answers should give you a quick way of answering #15

Just use the standard equations of kinematics.
Calculate the acceleration of car first.
Use it to find force.
Use that to find work.

(EDIT:crossed posts with tiny-tim and his shiny new avatar )

Okey dokey thanks for the help :) Sorry to spam up the forum thread! I am SO bad at physics!

laurenbaboran said:
Sorry to spam up the forum thread!

No, that's what it's there for!

Show us what you get