A CD has a mass of 17 g and a radius of 6.0 cm. When inserted into a player, the CD starts from rest and accelerates to an angular velocity of 22 rad/s in 0.88 s. Assuming the CD is a uniform solid disk, determine the net torque acting on it.
2006-11-15 23:14:44 · 2 answers · asked by Alan l 1 in Science & Mathematics ➔ Physics
Hi Alan the 1st!
We neglect the central aperture in CD, then inertia momentum is I=m*r^2/2 for any homogeneous disk, m=0.017kg, r=0.06m. Torq T=I*w’, w’ is angular acceleration, while w=w’*t, w=22 rad/s, t=0.88s, thus T=m*r^2*(w/t)/2, - plug in the proper numbers, be a good boy!
2006-11-16 06:28:16 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Rotational Inertia, I, of the disk is (M*R^2)/2. Units will be gm*cm^2.
The acceleration, alpha, that got it up to 22 rad/s in .88s:
alpha = (delta w)/(delta t). Units will be radians/s^2
The torque, tau, then
tau = I*alpha. Units will be gm*cm^2/s^2 (radians aren't a unit, so you can drop it). But you should convert to Newton*meters. To do so: convert the grams to Kg, and cm to m. Then a Kg*m/s^2 is a Newton.
2006-11-16 15:55:40 · answer #2 · answered by sojsail 7 · 0⤊ 0⤋