Double Checking a Bicycle Downhill Homework Problem

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SUMMARY

The discussion revolves around a physics homework problem involving a bicycle descending a hill. The total mass of the rider is 40 kg, with an initial speed of 5 m/s, a hill height of 20 m, and a friction force of 20 N. The calculations confirm that the speed at the bottom of the hill is approximately 14.7 m/s, derived from the conservation of energy principles, including kinetic energy (KE), potential energy (PE), and work done against friction.

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  • Understanding of kinetic energy (KE) and potential energy (PE) equations
  • Knowledge of work-energy principle
  • Basic algebra for solving equations
  • Familiarity with units of measurement in physics
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  • Study the impact of friction on motion in physics
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Aikenfan
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Homework Statement


I wasn't sure if i was doing this problem correctly, if anyone could double check for me, that would be great!
You ride your bicycle down a hill. Your total mass is 40 kg. At the top of the hill, your
speed is 5 m/s. The hill is 20 m high and 200 m long. If the force of friction is 20 N, what is
your speed at the bottom of the hill?






Homework Equations





The Attempt at a Solution


Top =
KE = 1/2 m v ^2
KE = 1/2 (40) (5)^2 = 500

PE = mgh
(40) (9.8) (20) = 7840

W = Fd
(20)(200)= 4000

7840 - 4000
=3840

3840 + 500 = 4340 = 1/2 (40) v ^2
divide both sides by 20
take the square root, and got 14.7 as my answer...
 
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Looks ok to me. Though I'd be more careful about putting units on things.
 
Last edited:

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