School of Physics Lecture Demonstration Manual

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.



Click on pictures to enlarge.

Moment Pic 1

Moment Pic 2


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.

Safety notes


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