Arena Table Exhibits KL28 Racing wheels


Do two wheels with the same shape rotate at the same speed?

Place the two wheels at the top edge of the angled plane and release them at the same time.

Both wheels are the same size and same weight. One of them, however, will always beat the other one. Can you find any differences between the wheels?

When a solid object rotates, all of the points on the object rotate around the same axis. One of the wheels has a heavy centre and the other wheel’s weight is located toward the outer rim, so the mass is distributed to different parts of the wheels. The moment of inertia signifies the inertia of the object as it rotates or, in other words, its ability to resist the rotational movement. The moment of inertia depends on an object’s mass and its distance from the axis of rotation. The closer the mass is to the axis of rotation, the lower the moment of inertia. Thus, the wheel with the heavier centre will always win.

The effect of the moment of inertia can be observed in a figure skater’s pirouette. First, when the skater spins with open arms, the moment of inertia is greater and the speed of rotation less. Drawing the arms close to the body causes the moment of inertia to decrease and the skater spins faster.

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