Work done on a stationary bicycle?

[vizakenjack]

So when someone is simply cycling on a stationary bike, is that person doing any work? Because work is Force * distance. But there's no distance here, right?

Is work simply the energy then?

 

[berkeman]

So when someone is simply cycling on a stationary bike, is that person doing any work? Because work is Force * distance. But there's no distance here, right?

Is work simply the energy then?

You are generating force with your legs to turn the pedals & crankshaft against a reactive force. Stationary bikes are designed to have a configurable resistance that they offer to your pedaling.

 

[CWatters]

Stationary exercise bikes usually turn the energy you produce into heat, perhaps heating a mass of air...

Work = mass * specific heat capacity * temperature change.

 

[vizakenjack]

Work = mass * specific heat capacity * temperature change.

But I thought work had to have distance?

So how come, when you cycle a regular bicycle on a road, you don't account for temperature change? You just do F*distance

 

[jbriggs444]

But I thought work had to have distance?

The pedals are moving.

 

[CWatters]

But I thought work had to have distance?

So how come, when you cycle a regular bicycle on a road, you don't account for temperature change? You just do F*distance

Energy is always conserved, its just converted from one form to another. The equations you can use to calculate the flow of energy in a system depends on the form of energy at that point in the system.

When you cycle a regular bike some of the total force is due to air resistance. Stirring the air heats it up. No need to account for this separately because its already included in the total force. Another part of the total force is due to rolling resistance an that heats the tyres. Again no need to account for that separately because its also included in the total force.

 

[CWatters]

Clearly there are times when you would like to know what fraction of force * distance is due to drag, rolling resistance, bearing friction etc and account for all the components separately.