What is the magnitude of the angular momentum of the 650 rotating bar in the figure
http://i27.tinypic.com/2lm2mbb.jpgWhat is the magnitude of the angular momentum of the 650 rotating bar in the figure?
Angular momentum L = I蠅, where
I = the moment of inertia about the axis of rotation, which for a long thin uniform rod rotating about its center as depicted in the diagram would be 1/12m鈩撀? where m is the mass of the rod and 鈩?is its length. The mass of this particular rod is not given but the length of 2 meters is. The moment of inertia is therefore
I = 1/12m*2虏 = 1/3m kg*m虏
The angular momentum 蠅 = 2蟺f, where f is the frequency of rotation. If the angular momentum is to be in SI units, this frequency must be in revolutions per second. 120 rpm is 2 rev/s, so
蠅 = 2蟺 * 2 rev/s = 4蟺 s^(-1)
The angular momentum would therefore be
L = I蠅
= 1/3m * 4蟺
= 4/3蟺m kg*m虏/s, where m is the rod's mass in kg.
The direction of the angular momentum vector - pseudovector, actually - would be straight out of the diagram toward the viewer.
Edit: 650 g = 0.650 kg, so
L = 4/3蟺(0.650) kg*m虏/s
鈮?2.72 kg*m虏/s
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