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welssen
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Homework Statement
In bicycling, each foot pushes on the pedal for half a rotation of the pedal shaft; that foot then rests and the other foot takes over. During each half-cycle, the torque resulting from the force of the active foot is given approximately by τ = τ0 sin ωt, where τ0 is the maximum torque and ω is the angular speed of the pedal shaft (in s-1 as usual). A particular cyclist is turning the pedal shaft at ω=70.0 rpm, and at the same time τ0 is measured at 38.5 N•m.
Find:
(a) the energy supplied by the cyclist in one turn of the pedal shaft and
(b) the cyclist's average power output.
Homework Equations
Work:
W = τθ, with θ the angular displacement;
Work-energy theorem:
W= ΔKE = Energy supplied by the cyclist
The Attempt at a Solution
For (a) I thought of using the work-energy theorem the following way:
E=τ0 sin(ωt)θ
with:
- θ=2π rad=one revolution
- t=θ/ω
So I get E = 38.5*sin(ω*2π/ω)*2π = 0 !
This is not really what I expect...
For (b) there may be a rotational version of P=F*v that is P=τω.
Thanks for your help