What is the angular momentum of a rod with a mass of 8kg and length of 4m that is spinning around its center at 12Hz?

1 Answer
Dec 23, 2016

The answer is 256π kgm2s which to the nearest whole number is 804 kgm/s

Explanation:

Angular momentum is similar in formula to linear momentum:

L=I×ω as compared to p=m×v

To find the moment of interia I, 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 I.

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

I=mL212

L being the length of the rod, and m its mass.

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

ω=24π

Put it together:

L=(mL212)×24π = (8)(42)(24π)12 = 256π kgm2s

which is approximately 804 kgm2s