MDCAT Physics · Physics · Circular and rotational motion. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
In rotation, moment of inertia I plays the part that mass plays in straight-line motion. It depends on the mass and on how far that mass is from the axis, so the same body has a different I about a different axis.
A spinning body has rotational kinetic energy ½Iω2 and angular momentum L = Iω. If no external torque acts, L stays constant. So when a body pulls its mass closer to the axis, I falls and ω rises.
A satellite stays in a circular orbit because gravity supplies the centripetal force. Its orbital speed depends only on the radius of the orbit and the mass of the planet, not on the mass of the satellite.
Students think rotational kinetic energy stays the same when a skater pulls her arms in. Angular momentum stays the same; the kinetic energy increases because she does work in pulling her arms in.
Answer: 5.0 revolutions per second (10π rad s−1).
Type what you are stuck on. The helper finds the explanation, worked examples and the notes to read, free and instant.
← Angular motion and centripetal forceViscosity and drag →Take a MDCAT Physics test