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# A disk of radius 7.2 cm and mass 0.41 kg is pulled along a frictionless surface?

A disk of radius 7.2 cm and mass 0.41 kg is pulled along a frictionless surface with a force of 13.1 N by a string wrapped around the edge 24 cm of string has unwound oﬀ the disk. At the instant shown the angular velocity is 19 rad/s. What is the magnitude of the angular momentum about the center of

the disc?

I know that you don't need the image to answer the question, because I didn't need it to. My only question is why doesn't the answer include translational momentum? The answer is 0.0201917, which is just the value for rotational momentum.

But isn't translational angular momentum also considered a part of "angular momentum"

### 1 Answer

- AlgolLv 79 years agoFavorite Answer
Because the question does not ask for the TOTAL momentum (rotational plus translational).

EDIT: As you know, the translational momentum of any point object (that is, the center of our disk in this problem) is p = mv and rotational (or angular) momentum is L = Iω. These are two separate types of momentum, the total momentum for the disk would be:

p(total) = mv + Iω