Question

Four equal masses m are so small they can be treated as points, and they are equally spaced along a long, stiff wire of neglible mass. The distance between any two adjacent masses is l. What is the rotational inertia I_cm of this system about its center of mass?
1) 1/2 ml^2
2) 3 ml^2
3) ml^2
4) 2 ml^2
5) 4 ml^2
6) 7 ml^2
7) 5 ml^2
8) 6 ml^2

Answer 1

Answer: 5m/L^2

Explanation:

Inertial I = mr^2 where r = distance from axis of rotation, while m is the mass of the object.

I = 2[m(1L/2)^2] + 2[m(3L/2)^2] = 2m×. 25/L^2+ 3m×2. 25/L^2= 0. 5m/l^2 +4. 5m/l^2

= 5m/l^2.