Hewitt Drewit
http://www.youtube.com/watch?v=8I4ii1xEeG0
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In this video, Hewitt tells us:
angular momentum = momentum times radial distance
angular momentum = mvr
An object or system of objects will maintain its angular momentum, unless acted upon by an external net torque.
gives us an example of this with planets and their moons
Shows a man spinning with weights pulling them out from his body (greater rotational inertia/ harder to spin) and in closer to his body (smaller rotational inertia/easier to spin).
also gives example of ice skaters spinning in this same manner
if no external net torque acts on a rotating system, the angular momentum of that system remains constant (conservation of angular momentum)
Hewitt leaves us with a question: One is at an amusement park, in the middle of a turntable, that is set spinning freely. If one crawls towards the edge of the turntable, does its rotational rate increase, decrease, or remain the same? What physics principle supports your answer?
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