In: Physics
As a physics demonstration, you want a special bowling ball made to demonstrate exactly 1 kg·m2, so that your students can rotate the ball about its center of mass to get a "feel" for how "big" 1 kg·m2 is. The bowling balls most familiar to your students has a weight of 15.4 pounds and have a circumference of 25.5 inches, but do not have a moment-of-inertia equal to 1 kg·m2. Since the sporting goods manufacturer has no understanding of how \"big\" 1 kg·m2 is, calculate the diameter of the demo bowling ball (in inches) it will need to manufacture. Assume that bowling balls are solid, with a constant density.
let r be the radius and m is the mass then the moment of inertia of a solid sphere is I = 2mr2 / 5
1 = 2/5 * ( 6.93 * r2) 1 pound = 0. 45 kg
r = 0.6 m 15.4 pounds = 6.93 kg
therefore the diameter should be d=2r = 1.2 m