- #1

kenway

- 13

- 1

1. Homework Statement

1. Homework Statement

"If you lift the front wheel of a poorly maintained bicycle off the ground and then start it spinning at 0.72rev/s, friction in the bearings causes the wheel to stop

in just 12s.

If the moment of inertia of the wheel about its axle is 0.30kg\m

^{2}, what is the magnitude of the frictional torque?"

2. Homework Equations

2. Homework Equations

I know:

Στ=Iα

α=Δω/Δt

I=mr

^{2}

## The Attempt at a Solution

Like I said, I have no idea how I am supposed to use the given variables to find friction.

This is an attempt I tried:

α=Δω/Δt

=0.72/12

=0.06m/s

^{2}

So I can now find torque with the angular acceleration:

∑τ=Iα

= (0.30kg/m

^{2})(0.06m/s

^{2})

= 0.018Nm

That's a small number that I'm pretty sure isn't right. Even if it is, I don't know where to go from here to find friction. If someone could just guide me/give me equations then I'd appreciate it

thanks!