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Rolling Friction of Bicycle Tires

  1. Oct 22, 2014 #1
    1. The problem statement, all variables and given/known data
    Two bicycle tires are set rolling with the same initial speed of 3.30m/s along a long, straight road, and the distance each travels before its speed is reduced by half is measured. One tire is inflated to a pressure of 40 psi and goes a distance of 17.3m ; the other is at 105 psi and goes a distance of 93.0m . Assume that the net horizontal force is due to rolling friction only and take the free-fall acceleration to be g = 9.80m/s2
    What is the coefficient of rolling friction μr for the tire under low pressure?

    2. Relevant equations
    Fx=ma
    Fx=μn
    n=mg
    v2=v02+2a(x−x0)

    3. The attempt at a solution

    First I solved for the acceleration:
    1.65^2 = 3.3^2 + 2a(17.3)
    a= -.24

    Then I set Fx=ma and Fx=μn to be equal, and substituted n=mg in for n
    ma=μmg
    The masses cancel out so I get
    a=μg
    I tried solving for this
    -.24=u(9.8)
    and got -.024, but this answer was incorrect.

    I feel good about this process but don't know I'm doing wrong? I found another question exactly like this on here but when I tried to do the calculations for acceleration I kept getting a different number, so I don't know if that's where my problem lies but if so I don't understand how my math is wrong.
     
  2. jcsd
  3. Oct 23, 2014 #2

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    Have a think about the concept of a negative coefficient of friction.
     
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