2 MCAT questions - friction

  • Thread starter cbrons
  • Start date
  • #1
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Homework Statement



1. A car moving at 20 m/s brakes and slides to a stop. If the coefficient of kinetic friction between the pavement and the tires of the car is 0.1, how far does the car slide?

A. 50 m
B. 100 m
C. 200 m
D. 400 m

2. A car moving at 20 m/s brakes and slides to a stop. If the coefficient of kinetic friction between the pavement and the tires of the car is 0.1, how much time is needed for the car to come to a complete stop?

A. 1 s
B. 10 s
C. 20 s
D. 40 s


Homework Equations



U(k)mgcos0

The Attempt at a Solution



Well the answers for both are C, as the back of the book states. The problem is, I don't understand how you can figure out either the time or distance with the information given... can anyone shed some light?
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
6,230
31
Use energy conservation for the first one, the work done by friction is the change in kinetic energy.
 

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