Physics of Angular Momentum
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Questions and Answers

What happens to the angular velocity of a neutron star during its collapse?

The angular velocity increases.

The units of angular momentum are __________.

kg*m^2/s

Which statement best describes the angular momentum of a merry-go-round when pushed to the left?

Viewed from above, the angular momentum would be negative.

The angular momentum of an object moving in a circle can be calculated using __________.

<p>I times omega or m times v times r</p> Signup and view all the answers

What can you say about the angular momentum of the minute hand and the hour hand of an analog clock?

<p>The minute hand has greater angular momentum than the hour hand.</p> Signup and view all the answers

Is angular momentum conserved for the turntable and putty during the process?

<p>True</p> Signup and view all the answers

Both hands of an analog clock have positive angular momentum.

<p>False</p> Signup and view all the answers

What happens to the block's speed when you pull the string decreasing its circular path radius?

<p>The block's speed increases.</p> Signup and view all the answers

In which process is the angular momentum of the object conserved?

<p>An ice-skater pulls in his arms causing him to spin faster.</p> Signup and view all the answers

If the wheels from two different kinds of cars have the same mass, same radius, and same angular velocity, they __________.

<p>might have the same angular momentum, but might not.</p> Signup and view all the answers

What is true about the merry-go-round's angular momentum while the dog is in the air?

<p>The merry-go-round has zero angular momentum, but the dog has non-zero angular momentum.</p> Signup and view all the answers

Just before the gear and disk make contact, what can be said about their angular momentum?

<p>They have the same angular momentum.</p> Signup and view all the answers

If some quantity, let's call it 'Z,' is conserved for a certain system, during a certain process, that must mean __________.

<p>any change in Z for parts of the system during the process is offset by an equal but opposite change for the Z of other parts of the system.</p> Signup and view all the answers

What happens to the total angular momentum of the system (turntable, professor, and dumbbells) during the brief process of lowering his arms?

<p>The total angular momentum is conserved.</p> Signup and view all the answers

Without external torques, an object __________.

<p>cannot change its own angular momentum.</p> Signup and view all the answers

Without external torques, an object __________.

<p>can change its own angular velocity by rearranging its mass distribution.</p> Signup and view all the answers

What is true when two kids grab onto each other while sliding on ice?

<p>Their total angular momentum is constant.</p> Signup and view all the answers

After they make contact, what can be said about the gear's angular momentum compared to the disk's?

<p>The gear has an angular momentum with a larger magnitude than that of the disk.</p> Signup and view all the answers

After getting a flat tire, how does the lighter wheel's angular momentum compare to the other wheels on the car?

<p>It will have a smaller magnitude.</p> Signup and view all the answers

The magnitude of the angular momentum of a rotating wheel can be directly calculated using __________.

<p>L = I times omega.</p> Signup and view all the answers

The angular momentum of a system is conserved during a process only if __________.

<p>no net external torque is exerted on the system.</p> Signup and view all the answers

After the dog has landed and the merry-go-round is spinning, what is true about their angular momentum?

<p>Both the merry-go-round and the dog have non-zero angular momentum around the merry-go-round's axle.</p> Signup and view all the answers

Study Notes

Neutron Stars and Angular Momentum

  • During collapse, a neutron star's angular velocity increases due to conservation of angular momentum.
  • Angular momentum remains constant in the absence of external torque.

Units of Angular Momentum

  • Angular momentum units are kg*m²/s.
  • Linear momentum units differ (kgm/s), while kgm/s² denotes force.

Angular Momentum Direction

  • When pushing a merry-go-round to the left, its angular momentum appears negative when viewed from above.

Calculating Angular Momentum

  • For circular motion, angular momentum formula can be I * ω or m * v * r, where I is rotational inertia, ω is angular velocity, m is mass, v is speed, and r is the radius.

Clock Hands Comparison

  • The minute hand of an analog clock has greater angular momentum than the hour hand due to higher angular velocity and greater moment of inertia.

Conservation of Angular Momentum in Systems

  • A turntable's angular momentum remains conserved when putty sticks to it as no external torque is applied.
  • Angular momentum of a system is conserved if no net external torque acts on it.

External Forces and Systems

  • The scenario of two kids grabbing onto each other while sliding on ice maintains a constant total angular momentum.

Interaction of Gear and Disk

  • A gear and disk, prior to contact, have the same angular momentum due to their angular speeds and moments of inertia relation.

Effects of Mass on Angular Momentum

  • A lightweight wheel on a car will have a smaller angular momentum compared to the heavier, identical wheels when in motion.

Rotational Dynamics

  • The angular momentum magnitude for rotating objects is calculated via L = I * ω, as each part of a rigid body has diverse properties.

Non-zero Angular Momentum Scenarios

  • After a boy on a merry-go-round catches his dog, both the boy and the merry-go-round possess non-zero angular momentum due to their circular motion.

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Description

Explore the key concepts of angular momentum, its conservation, and practical examples like neutron stars and clock hands. This quiz covers calculations, units, and directionality of angular momentum in various systems.

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