# How do you add angular momentum in different dimensions?

1. Aug 10, 2015

### 24forChromium

Say a ring is spining around the z-axis, an angular impulse is then applied to it in the x-axis, what is the resultant motion qualitatively and quantitatively? How can it be calculated?

(You can make up the quantity of z-angular momentum and x-angular impulse)

2. Aug 10, 2015

### dipole

I assume you mean that the impulse is delivered when the ring is perfectly in the x-z plane. Initially the ring has angular momentum $\vec{L} = \omega_z\hat{z}$, and the impulse introduces some angular momentum $\omega_x\hat{x}$. The total angular momentum will then be the vector sum of these:

$\vec{L'} = (\omega_x, 0, \omega_z)$, and given the rotational symmetry of the ring, it will start to rotate about an axis parallel to this new vector, which now lies in the x-z plane. If the ring is spinning on a table, for example, then there is the additional complication of torque on the ring due to gravity, and it will precess about this axis.

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