Mi-5 Moment of Inertia
Published: Thursday 09 March 2006 - Updated: Thursday 24 March 2011
To demonstrate the dependence of the moment of inertia on the distribution of mass with respect to the axis of rotation.
- Rotor with slideable masses on long light tube and drive pulley
- Thin string and weight
Click on pictures to enlarge.
Moment of Inertia 1
Moment of Inertia 2
With masses fixed at maximum R, show the (slow) angular acceleration of the sytem resulting from torque exerted by the tension in the string. Set masses at minimum R and repeat, showing much higher angular acceleration with (approximately*) the same torque.
*Note: Strictly speaking torque is not quite constant because of variation of string tension T=m(g-a), but, because b has been chosen <<Rmin, a<<g for all R's.