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Work, Force, Brakes

  • #1

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!!
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
25,832
250
hi laurenbaboran! :wink:

let's start with #15:

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 :smile:
 
  • #3
662
307
Just use the standard equations of kinematics.
Calculate the acceleration of car first.
Use it to find force.
Use that to find work.
:wink:
(EDIT:crossed posts with tiny-tim and his shiny new avatar :smile:)
 
  • #4
Okey dokey thanks for the help :) Sorry to spam up the forum thread! I am SO bad at physics!
 
  • #5
tiny-tim
Science Advisor
Homework Helper
25,832
250
Sorry to spam up the forum thread!
No, that's what it's there for! :wink:

Show us what you get :smile:
 

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