Posted by **eddy** on Thursday, February 18, 2010 at 7:52pm.

the driver of a 1200 kg car notices that the car slows from 20 m/s to 15 m/s as it coasts a distance of 130 m along level ground. how large a force opposes the motion? (book answer .81 kN )

can you help me plug the numbers into the correct formula to use for this question.

- College Physics -
**bobpursley**, Thursday, February 18, 2010 at 7:57pm
College physics is not about plugging numbers into the correct formula. It is about analyzing, and using a math model to predict an outcome.

Here energy comes to mind. Some force over some distance is absorbing kinetic energy from the car.

Intial KE-FinalKE=Force*distance

1/2 mvi^2-1/2mvf^2=Force*130

solve for force.

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