Moment of inertia

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The race between the hoop and the disk is a classic race in physics. If a hoop and a disk of equal mass and radius, as shown in the picture, are placed at the top of an inclined plane and released, which will get to the bottom of the ramp first?

Newton's second law for rotation helps us predict a winner. The moment of inertia of an object provides resistance to a rotational force in the same way the mass of an object resists linear acceleration. If we inspect the moment of inertia for the disk and the hoop in the above image we find that the disk has half the moment of inertia of a hoop of equal mass. Since it has less resistance to rotation, it will speed up quicker and get to the bottom of the ramp first as seen in the movie.

1. Try the race with two equal size cans, one filled with liquid (soup broth) and the other with a solid (cranberry sauce or dog food). Which can wins the race?
2. Why is the moment of inertia smaller of the disk smaller than the moment of inertia of the hoop?