Moment of Inertia and Angular Momentum

Moment of Inertia and Angular Momentum

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Open Ended

Where have we seen angular momentum at work before? Explain it.

Moment of Inertia

• An object with a large moment of inertia is difficult to start or stop rotating.

• Moment of inertia is to rotational motion, what inertial mass is to linear motion.

• Moment of inertia is found by I=mr²

• For different objects there are some varitations to the equation

• Normally the more distributed or closer to the center of mass that the mass of the object is the smaller the moment of inertia

Discussion: Write your notes

A disk and a hoop of the same mass and radius are released at the smae time at the top of an inclined plane. Does the disk reach the bottom of the plane before, after, or at the same time as the hoop?

Angular momentum

• L=Iw

• L= mass x r x w

Open Ended

Is it easier or harder to turn something if you are closer to the axis of rotation?

Torque

• torque= radius x F - straight line objects ie. wrench

• physical quantity that causes rotation

• torque= radius xF x sinθ

• Moment arm- shortest distance between axis of rotation and line of force.

• moment arm = r sinθ

• torque= moment arm x F

• torque= moment of inertia x angular acceleration