# Moment of inertia / torque question

1. Dec 11, 2005

### ptlffrty

Deleted Deleted

Last edited: Dec 12, 2005
2. Dec 12, 2005

### emptymaximum

ummm. i think you mean to say it is attached to a solid 'brick'
$$\vec{\tau} = \vec{r} \times \vec{F}$$
where $\vec{r}$ is the position vector from the axis of rotation to where the force is acting, and $\vec{F}$ is the force.
the direction of the vector produced by the cross product is given by the right hand rule.

3. Dec 12, 2005

### ptlffrty

oops. i meant disk.

Last edited: Dec 12, 2005
4. Dec 12, 2005

### ptlffrty

bump bump bump

5. Dec 12, 2005

### ptlffrty

anyone? anyone?

6. Dec 12, 2005

### ptlffrty

7. Dec 12, 2005

### PhY_InTelLecT

One qn.. How did u actually arrive at this?

Last edited: Dec 12, 2005
8. Dec 12, 2005

### ptlffrty

added the moment of inertia of the hoop (mr^2) witht he moment of inertia of the disk (.5mr^2).. good chance its wrong, but itdoesnt really matter at this point, i just turned the assignment in a few minutes ago

9. Dec 12, 2005

### PhY_InTelLecT

Moment of inertia shld be the same as the formula for torque=F*d=mgd.
I'm not sure bout it either. But are u sure mr^2 is the right formula for moment of a force?

10. Dec 12, 2005

### FredGarvin

You deleted the original question. How are we going to help if we don't know what you are asking? However, if it is a homework problem, it belongs in the homework section.