Physics 8: 6-9 Rotational Kinetic Energy
Text Reading: Giancoli, Physics - Principles with Applications, Chapter 8: 6-9
- 8.7: We've covered the rotational equivalents of kinematics and dynamics. Now we just do the same thing with kinetic energy and angular momentum, using angular velocity and moment of inertia in the same relationships as we used linear velocity and mass.
Rotational kinetic energy = 1/2 I ω2. To use this, we have to recognize that something can have rotational kinetic energy if it is spinning or rolling and translational kinetic energy if its center of mass is changing position. The two can be separately calculated.
- 8.8: Angular momentum is conserved, just like linear momentum. If no outside torque acts on an object to change its rotational speed or direction, its angular moment remains unchanged. Note that a linear force can act on the object to speed up or slow down or change its linear velocity without changing the angular motion of the object.
- 8.9: The right hand rule tells us the direction of the result of angular momentum and torque calculations. This is a vector at right angles (out of the plane) in which the original vectors lie. To figure the direction of angular momentum, put your wrist at the center of rotation, point your fingers out along the radius, then curl them in the direction of rotation. Extend the thumb in a hitch-hiking gesture. The thumb now points in the direction of the angular momentum vector.
|KEtranslational = ½mv2
||KErotational = ½Iω2
|p̅ = mv̅
||L̅ = Iω̅
Read the following weblecture before chat: Inertia, Acceleration, and Force
Use the physics simulation ==>HERE<==
to experiment with angular momentum.
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