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Static friction in rolling
Intermediate
Friction enables rolling but does no work in pure rolling.
Static friction at the contact point prevents slipping and may point either way depending on acceleration. In pure rolling at constant speed it is zero and does no work.
On an incline it points up the slope.
Rolling resistance is a different thing.
In more detail
In rolling, static friction at the contact point provides the torque that changes the rotation of the body. It does no net work when rolling without slipping, but it does redistribute energy.
Real-world uses
- Car wheels accelerating from rest rely on static friction at the road.
- Ball rolling down a slope needs friction to start rotating.
- A car wheel that rolls without skidding relies on static friction at the contact point, which does not dissipate energy.
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Frequently asked questions
Does static friction do work when rolling?
Not when rolling without slipping, because the contact point is momentarily at rest.
Can friction be too small?
Yes. Insufficient friction causes the body to slip rather than roll.
Does friction do work on a rolling wheel?
In pure rolling, the contact point is at rest, so friction does no work, which is why rolling wheels lose little energy.
Related topics in Rotational Motion
Atwood with real pulley · Yo-yo and unwinding cylinder · Angular impulse · Slipping to rolling transition · Bohr angular momentum