Static friction can cause rolling without doing work

01
The tempting model
Assuming any friction force always removes mechanical energy.
02
Why it feels right
Friction is usually introduced as dissipative.
03
Where it breaks · how to catch it
You subtract friction work for a rigid body rolling without slipping on a fixed surface.
04
The correct model
For ideal rolling without slipping on a fixed surface, the contact point is instantaneously at rest, so static friction does no work. It can redistribute energy between translation and rotation.
05
Repair · see it, then test it
worked example A solid sphere rolls down a rough incline without slipping. Does static friction dissipate energy?
Tempting move
Yes, because friction acts.
Correct move
No ideal dissipation; static friction provides torque while doing zero work at the contact.
Test the repair ROT-06 · transfer

A wheel rolls without slipping on a fixed road. In the ideal rigid-body model, static friction at the contact point:
Must dissipate energy Can provide torque while doing zero work Must point backward Must be zero

Make a fresh prediction before referring to the worked example.
Then practise it on the ladder
R35Static friction in rollingadds: Static friction can provide torque without dissipating energy.R39Rolling down an inclineadds: Rolling inertia reduces translational acceleration.R50The rolling raceadds: In rolling, the inertia ratio β = I/MR² decides everything; mass and radius cancel.