Rotational Motion

Rotational motion is similar to linear motion in many ways. Here is a worksheet and a presentation on the basic equations for rotational motion, and a movie demonstrating torque. It really isn't as difficult as Calvin thinks it is. Here is a cool movie of Whirling Dervishes.

Centripetal force is the force towards the center of a circle that makes an object move around the circle. If you imagine a free body diagram while looking at this picture of a speed skater or video of motor cycle, you should be able to see that the total force is towards the center of the circle. There is a presentation on circular motion and acceleration and a worksheet that should make it even clearer, and there is also a movie about centripetal force related to roller coasters.

The tricky thing about centripetal force is that it feels like there is a force pulling you to the outside of the curve when you go around a circle, but that is actually just your inertia. This phenomena could be used to create artificial gravity in space. Here is a movie of it being used on Earth, and two movies of it being used in space. Here are a science fiction movie and two pictures with artificial gravity.

The moment of inertia of an object is a measure of how easy it is to rotate an object. How far the mass is from the center of rotation effects how easy it is to rotate. Here are two movies of objects rolling down ramps. The fastest objects are the ones that rotate the easiest. There is also a video of a man rotating some rods. Why is one rod more difficult than the other?

Angular momentum is conserved, which means that if there is no outside force, the angular momentum can't change. Because of this you can change your angular velocity simply by changing your moment of inertia. This is called the dumbell effect. Here are three (1 2 3) movies of the dumbell effect in a classroom, and two movies (1 2) of Michelle Kwan using the dumbell effect to spin faster while figure skating.

This video doesn't have much to do with rotational motion, but how does he do that?!