This year, Thanksigiving and Hannukah share a night and the holiday has been named Thanksgivingkuh. This won’t happen again for another 70,000 years so in its honor I am looking at the physics behind a dreidel. The question I asked was how much rotational kinetic energy does a small plastic dreidel have when it is initially spun?
KErot = ½ Iω2
To calculate the moment of inertia of the dreidel I approximated it as a solid cylinder which is not entirely correct but I think it was the best option. The mass of a plastic dreidel is about 0.00907 kg according to a source online. The diameter of the dreidel was approximately 1 inch which makes the radius is 0.0127 meters.
I= ½ mr2
I= ½ (0.00907kg)(0.0127m)2
The initial angular velocity of the dreidel--it rotated approximately 3 rotations per second, therefore:
3 rotations x (2π radians / one rotation) = 18.85 radians/second
Therefore the total rotational kinetic energy of the dreidel when it was initially spun is:
KE = ½ (7.314x10-7)(18.85)2 = 1.299 x 10-4 J