Why is there no work for someone walking on flat plane

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zanick said:
rolling can still have friction.. "rolling without friction" allows you to calculate the work used strictly to move the object from one point to another.
If it's rolling, the presence or absence or degree of friction with the surface makes no difference. You may be thinking of rolling resistance.
 
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haruspex said:
If it's rolling, the presence or absence or degree of friction with the surface makes no difference. You may be thinking of rolling resistance.
Yes, I am speaking of rolling resistance... is there any other kind that wouldn't make a difference? :)
also, I guess you could consider the extra rotational inertia of the rotating elelments as well ( WR^2)
 
zanick said:
Yes, I am speaking of rolling resistance... is there any other kind that wouldn't make a difference? :)
If there's rolling resistance, that will apply equally with or without friction. The difference is that with friction both rotational and translational speeds will fall (in step); without friction only the rotational speed is affected - but as soon as that happens it is no longer considered rolling.
 
haruspex said:
If there's rolling resistance, that will apply equally with or without friction. The difference is that with friction both rotational and translational speeds will fall (in step); without friction only the rotational speed is affected - but as soon as that happens it is no longer considered rolling.
never hear about this type of stuff, would it only be affected without friction if the ball was not a perfect sphear? if not how would it lose any rotational speed?
 
Jewish_Vulcan said:
never hear about this type of stuff, would it only be affected without friction if the ball was not a perfect sphear? if not how would it lose any rotational speed?
It's not the shape, more the rigidity.
Real world objects are not completely rigid. A tyre deforms as it rotates, producing a flat area in contact with the road. This constant deformation takes work. But rolling resistance is not limited to that. It might be mostly that, but the term is a catch-all encompassing other losses as such axle friction.
 
haruspex said:
It's not the shape, more the rigidity.
Real world objects are not completely rigid. A tyre deforms as it rotates, producing a flat area in contact with the road. This constant deformation takes work. But rolling resistance is not limited to that. It might be mostly that, but the term is a catch-all encompassing other losses as such axle friction.
I was referring to, rolling friction being illuminated, but still the force to accelerate the mass translationally and rotationally and then to decelerate it, would be needed to calculate the work done over time. (power).
 
zanick said:
I was referring to, rolling friction being illuminated,
I guess you mean eliminated.
zanick said:
but still the force to accelerate the mass translationally and rotationally and then to decelerate it, would be needed to calculate the work done over time. (power).
You've lost me.