M-Rot 1: Effects of moment of inertia

PIRA: 1Q10.30

Equipment: Inclined plane (not very steep), meter stick, selected objects to roll down the incline: cylinders of the same size but different density, spheres of same diameter and same density as cylinder, hollow cylinder and solid cylinder of same density material and same outer dimensions, spheres of different diameters but same density, one pair of special composite cylinders. The inclined plane is on top of Set 8, Cabinet 1 and the objects are in a box in Set 9, Cabinet 3, Shelf 3.

Procedure: The paired composite objects are rolled down the incline. Each is made of equal masses of wood and iron. They have the same total mass, the same outer diameter, the same length. In one the iron is the inner cylindrical core while the wood makes an outer cylindrical shell. In the other the role of the wood and iron are reversed.

Tell the students you will allow a pair of selected objects (such as the composite pair just described) to run a race down the incline from an even start. Ask: How many think a certain one (such as the one with the iron shell) will win? How many think the other will win? How many think the race will be a dead heat? How many don't think?) Tally the results and start the race by resting the competing objects against the meter stick laid and held flat across the inclined plane. To start the race fairly remove the meter stick by a rapid translational motion down the plane.