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I'm currently trying to learn kinematics and I can't figure out what seems to be a basic problem. It is the following: An 1800 kg car brakes from 15 m/s to a stop in 3 seconds. What is the net force of friction on the tires?

If you could help describe how I could figure this out or give me hints I would be very happy. Thanks :D!

excal
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  • I'm voting to close this question as off-topic because this is a physics question and has absolutely nothing to do with programming. – meowgoesthedog Apr 09 '18 at 18:22
  • I'm voting to close this question as off-topic because it is about [physics.se] instead of programming or software development. – Pang Apr 12 '18 at 09:13

1 Answers1

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in SI units;

Suppose tires give constant force so acceleration is constant:

acceleration = (0-15)m/s/3s = -5m/s^2; force = acceleration * mass = -5*1800 = -9000 Newton

check 1: acceleration is about -0.5g so force is about -0.5*1800 kilopond = -900 kilopond = about -9000 Newton

check 2: friction is about half weight of car so friction coefficient has to be at least 0.5, table says this is possible if road is dry

Mats Lind
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  • Thanks a ton! I was trying to figure out how to find Ff but I forgot the only thing stopping the car would be friction. :D – excal Apr 10 '18 at 00:10