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.

Update:

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

1 Answer

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  • Algol
    Lv 7
    9 years ago
    Favorite 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

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