Three objects,a hoop,a disk,and a solid sphere start from the top of a hill and roll without slipping down to the bottom.Which one of the following statements is true?
A)The sphere reaches the bottom first.
B)The disk reaches the bottom first.
C)The object with the greatest mass reaches the bottom first.
D)All three reach the bottom at the same time.
E)The hoop reaches the bottom first.

Question

Three objects,a hoop,a disk,and a solid sphere start from the top of a hill and roll without slipping down to the bottom.Which one of the following statements is true? 
A)The sphere reaches the bottom first. 
B)The disk reaches the bottom first. 
C)The object with the greatest mass reaches the bottom first. 
D)All three reach the bottom at the same time. 
E)The hoop reaches the bottom first.

Quizplus · Accepted Answer

This is because the sphere has the lowest moment of inertia out of the three objects, which allows it to gain speed faster while rolling down the hill. The hoop, on the other hand, has a higher moment of inertia and is more likely to wobble and lose speed while rolling, while the disk has a moderate moment of inertia. The mass of the objects does not affect their speed down the hill as much as their moment of inertia does. Therefore, the sphere will reach the bottom first.

Three Objects,a Hoop,a Disk,and a Solid Sphere Start from the Top