Mistake Master
Mistake Master · AP Physics 1 · Unit 5 · Step-Through Animation
Rotational Inertia: Where the Mass Lives
You'll learnthat rotational inertia depends on how far the mass sits from the axis, squared.
Torque is the rotational push. This is the rotational stubbornness — and unlike mass, it isn’t fixed. Slide a bead, hop an axle, race a hoop against a disk, and watch I = Σmr² decide everything.
ROTATION LAB
Before you start
What you're looking at
Two 1 kg beads on a spinning rod, each 1 m from the central axis, beside a bar reading the system’s rotational inertia.
The question
What makes a thing hard to spin, if not simply its mass?
Watch for
How far each bead sits from the axis, since that distance enters squared; predict what happens if a bead slides outward.
What the symbols mean
The two violet beads carry the mass; the rotational-inertia bar reads in kg·m²; the axis is the marked center.
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