What is the angular momentum of a rod with a mass of 8 kg8kg and length of 4 m4m that is spinning around its center at 12 Hz12Hz?

1 Answer
Dec 23, 2016

The answer is 256pi256π kgm^2/skgm2s which to the nearest whole number is 804 kgm^/skgm/s

Explanation:

Angular momentum is similar in formula to linear momentum:

L=IxxomegaL=I×ω as compared to p =m xx vp=m×v

To find the moment of interia II, most students would check a list of known expressions, as every different geometry and even a different axis of rotation will play a part in determining the nature of II.

In the case of a rod being rotated about its centre, the moment of inertia is

I=(mL^2)/12I=mL212

LL being the length of the rod, and mm its mass.

The angular velocity omegaω is equal to the number of radians swept out by the rod each second. In this case, as each revolution equals 2pi2π radians,

omega=24pi ω=24π

Put it together:

L=((mL^2)/12)xx 24piL=(mL212)×24π = ((8)(4^2)(24pi))/12(8)(42)(24π)12 = 256pi" " kgm^2/s256π kgm2s

which is approximately 804 kgm^2/skgm2s