Purpose:Demonstrates effect of rotational inertia on acceleration of an object
A solid disc and a thin ring having the same mass and the same radius roll down an incline starting at rest from the same position. The roller with the greater moment of inertia, in this case the ring, rolls more slowly.
• When presenting the demonstration, encourage students to make a prediction before showing the roll. Will the two objects reach the bottom at the same time, or will one get there first? Which one?
The effect of rotational inertia on the speed of a rolling object can be confusing to new students, especially those who have just recently internalized the principles of linear motion. Having just un-learned misconceptions about objects in free fall and discovered that objects experiencing the same force fall at the same rate regardless of mass, it can be counterintuitive to realize that the corollary does not apply in rotational motion. The distribution of mass does itself affect the torque on an object and how fast it rolls.