In Fig. 11-45, three particles of mass m = 2.6 kg are fastened to three rods of
ID: 2262674 • Letter: I
Question
In Fig. 11-45, three particles of mass m = 2.6 kg are fastened to three rods of length d = 0.79 m and negligible mass. The rigid assembly rotates about point O at angular speed ? = 7.2 rad/s. About O, what are (a) the rotational inertia of the assembly, (b) the magnitude of the angular momentum of the middle particle, and (c)the magnitude of the angular momentum of the assembly?
Explanation / Answer
a) I = md^2 + m ( 2d ) ^2 + m ( 3d ) ^2 = 14 m d^2
I = 14 * 2.6 * 0.79^2 = 22.717 kg m ^2
b) L ( middle particle) = I ? = m( 2d ) ^2 * ?
L = 4 m d^2 ? = 4 * 2.6 * 0.79^2 * 7.2
L = 46.7326 kg m^2 s^-1
c)L ( assmebly ) = I ?
L = 22.717 * 7.2 = 163.5624 kg m^2