# Torque require to rotate ball

1. Mar 8, 2013

### sushilshinge

I want to calculate the torque required to rotate a ball.
1. Ball is solid having mass M kg.
2. Ball is bored through about its axis.
3. Ball is rotating about the axis XX

Please see attached file.

#### Attached Files:

• ###### Ball.bmp
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Last edited: Mar 8, 2013
2. Mar 8, 2013

### crissyb1988

You must find the moment of inertia of a hollow cylinder which is,
$$I=1/2 m ( r_i^2 + r_0^2)$$
r_i and the r_0 are radial distances from centre.

Than the relationship between torque, moment of intertia and angular acceleration, which is,
$$T=I \alpha$$

Now looking at the picture im not sure if ur including those caps on the top and bottom. In which case you must find their moment of intertia and add it to the cylinder

3. Mar 9, 2013

### sushilshinge

Right side view is a section of a ball. The hatching part is a solid part of ball.When you will cut the ball in left view in middle then by looking left side it will look like in right view.

4. Mar 9, 2013

### crissyb1988

Not sure I completely understand what your saying. Are the equations what you are after? Just find the moment of inertia of the top and bottom parts, if indeed Im understanding you correctly