Rotational Inertia Wands


Students twirl equal mass wands, one with the mass at the ends and the other with the mass at the middle. The moment of inertia is found to depend on the shape.




Principles Illustrated

While the shape of an object is not important for translation, it is critical for rotation of an object.

Worksheet: Moving_and_Spinning.pdf

NCEA & Science Curriculum

PHYS 3.4



Construct as shown in the photo of the apparatus. Have students verify that the force required to move the apparatus back and forth does not depend on the location of the masses, but the torque required to rotate the apparatus does. These are 1 Kg masses and the rod is from an equipment stand. Four clamps are required for each setup. A set of instructions for use by students is included under other materials below.  This demo is used in Phys 114 Lab as a warm-up.

Photo of the apparatus in use:



Apparatus_four_clampsCloseupBe sure to use four clamps as shown above and at left. The mass can slide into a student’s hand and cause a nasty pinch if the inner clamp is omitted.

Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.

Related Resources

Teaching Resources

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PIRA 1Q10.10


This teaching resource was developed with support from

The MacDiarmid Institute
Faculty of Science, Victoria University of Wellington
School of Chemical and Physical Sciences, Victoria University of Wellington


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