Angular momentum
Question:

A rotating rigid body have an angular momentum $\underset{L}{\rightarrow}$ which is equal to the product of $I$$\underset{\omega }{\rightarrow}$ where $I$is the moment of inertia and $\underset{\omega }{\rightarrow}$ is the angular velocity.
If a rigid-body spins along its main Axes it will continue spinning unless there is a torque  $\underset{\tau }{\rightarrow}$ acts on it.
A torque equals to the vector product of $\underset{F}{\rightarrow}$ x $\underset{r}{\rightarrow}$ where  $\underset{F}{\rightarrow}$ is the force and $\underset{r}{\rightarrow}$is the distance from the rotation axis and its direction is acording to Right - hand grip rule.

When a torque $\underset{\tau }{\rightarrow}$ acts on a rotating rigid body it will change the value and the direction of the angular momentum, $\underset{\Delta L}{\rightarrow}$/$\Delta t$=$\underset{\tau }{\rightarrow}$  (see animation 1)

### How do you think the disk motion will be?

1 People tried to answer this question

 The disk weight will cause a torque that will change the angular momentum and will cause an addition rotation (precession) around the y axis.
 The angular momentum will cause the disk to stay at the same place until it stopsand fall dawn.
 The weight of the disk will cause it fall down.
 The angular momentum of the rotating disk will resist changing in its direction so the disk have to continue rotating at the same place.

Fantastic :-)

Wrong answer:-(remember there is no friction

 Points on map: