Angular momentum conservation

In summary, the problem involves a person standing on a freely rotating platform and holding a spinning bicycle wheel. The moment of inertia of the person and platform is IP, while the wheel has a moment of inertia Iw and angular velocity WW. When the person moves the wheel's axis vertically, the angular velocity of the platform, WP, is unknown. The angular momentum is conserved in the vertical axis due to the absence of external forces, but external forces prevent the platform from rotating horizontally. This means that the conservation of angular momentum cannot be applied in the horizontal axis.
  • #1
hitemup
81
2

Homework Statement



A person stands on a platform, initially at rest, that can rotate freely without friction. The moment of inertia of the person plus the platform is IP. The person holds a spinning bicycle wheel with its axis horizontal. The wheel has a moment of inertia Iw and angular velocity WW. What will be the angular velocity WP of the platform if the person moves the axis of the wheel so that it points vertically upward?

Homework Equations


[/B]
L_initial = L_final

The Attempt at a Solution



I didn't understand why the angular momentum is conserved only in vertical axis. There is no external force, so what has happened to angular momentum in the horizontal? Wıth regard to what should I choose an axis so that I can apply the conservation?
 
Last edited:
Physics news on Phys.org
  • #2
hitemup said:
There is no external force, so what has happened to angular momentum in the horizontal?
External forces do come into play to prevent the platform from rotating horizontally. The platform is constrained to freely rotate only about a vertical axis.
 
  • Like
Likes hitemup

1. What is angular momentum conservation?

Angular momentum conservation is a fundamental principle in physics that states that the total angular momentum of a system remains constant in the absence of external torques. In other words, the amount of rotation of an object or system will not change unless a force is applied to it.

2. How is angular momentum conserved?

Angular momentum is conserved through the principle of inertia, which states that an object will maintain its state of motion unless acted upon by an external force. This means that a rotating object will continue to rotate at a constant speed and direction as long as no external torque is applied.

3. What are some examples of angular momentum conservation in everyday life?

One common example of angular momentum conservation is seen in ice skaters. As they spin, they pull their arms and legs closer to their body, decreasing their moment of inertia and causing them to spin faster. This is due to the conservation of angular momentum, which states that the total angular momentum of the skater must remain constant.

4. How does angular momentum conservation relate to the conservation of energy?

Angular momentum conservation is closely related to the conservation of energy. In fact, angular momentum conservation can be derived from the conservation of energy, as the two principles are fundamentally linked. This is because angular momentum is a type of energy known as rotational energy.

5. What is the significance of angular momentum conservation in the field of physics?

Angular momentum conservation is a crucial principle in the field of physics, as it helps to explain many phenomena in the natural world. It is used to understand the movements of planets, the rotation of celestial bodies, and the behavior of particles at the quantum level. Without angular momentum conservation, many physical processes would be difficult to explain and understand.

Similar threads

Which system to apply conservation of momentum to?
    • Introductory Physics Homework Help
Replies
2
Views
804
Collision between asteroids
    • Introductory Physics Homework Help
10
Replies
335
Views
8K
Change in Angular Velocity While Orbiting With No Torque
    • Introductory Physics Homework Help
Replies
30
Views
2K
Find velocities when a mass leaves a system of a rod with two masses
    • Introductory Physics Homework Help
Replies
10
Views
904
A planet of mass M and an object of mass m
    • Introductory Physics Homework Help
Replies
6
Views
693
Why is mechanical energy not conserved in this setup? (frictionless spinning cylinder's motion is changed)
    • Introductory Physics Homework Help
Replies
6
Views
333
Determining $L_{o}$: Finding Angular Momentum of System
    • Introductory Physics Homework Help
2
Replies
45
Views
2K
Simple Ice Skater with Conservation of Angular Momentum
    • Introductory Physics Homework Help
Replies
4
Views
1K
How Do You Correctly Cancel Angular Momentum in Physics Problems?
    • Introductory Physics Homework Help
Replies
3
Views
221
Angular momentum / conservation of momentum questions
    • Introductory Physics Homework Help
Replies
23
Views
1K

Hot Threads

Recent Insights

Back
Top