Kinetic Friction Video Lessons

Concept

# Problem: Two bicycle tires are set rolling with the same initial speed of 3.80 m/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 18.6m ; the other is at 105 psi and goes 92.6m . Assume that the net horizontal force is due to rolling friction only.What is the coefficient of rolling friction (Uk) for the tire under high pressure?

###### FREE Expert Solution

Uniform accelerated motion (UAM) equations, a.k.a. "kinematics equations":

Kinetic friction:

$\overline{){{\mathbf{f}}}_{{\mathbf{k}}}{\mathbf{=}}{{\mathbf{\mu }}}_{{\mathbf{k}}}{\mathbf{N}}{\mathbf{=}}{{\mathbf{\mu }}}_{{\mathbf{k}}}{\mathbf{m}}{\mathbf{g}}}$

Newton's second law:

$\overline{){\mathbf{\Sigma }}{\mathbf{F}}{\mathbf{=}}{\mathbf{m}}{\mathbf{a}}}$

For the tire at high pressure:

• a = ?
• Δx = 92.6 m
• v0 = 3.80 m/s
• vf = 3.80/2 = 1.90 m/s
• Δt = ?

vf2 = v02 + 2aΔx

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###### Problem Details

Two bicycle tires are set rolling with the same initial speed of 3.80 m/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 18.6m ; the other is at 105 psi and goes 92.6m . Assume that the net horizontal force is due to rolling friction only.

What is the coefficient of rolling friction (Uk) for the tire under high pressure?