Measuring Angular Momentum Changes in a Rotational Inertia Experiment

In summary, the angular velocity or speed goes either up or down with the angular momentum remaining the same. The only way to measure the angular momentum is to transfer it to a "reference" body.
  • #1
massb
1
0
In my experiment based on the inertia the angular velocity or speed goes either up or down with the angular momentum remaining the same. I understand that when a person is rotating to change the inertia you would either extend or detract the arms and legs (think dancer). I understand this concept and even somewhat how the calculate it except my angular momentum.

L=Iw since my inertia is changing how do I find the changing w(angular momentum) if I don't know the value of the L(angular momentum) yet. Would I just physically count the number of rotations per second in radians for each time the inertia is changed?
 
Physics news on Phys.org
  • #2
Hi welcome to phy forum(everyone does that so i did it too for your first post)
Well you don't know the L now but i hope that you know the speed at which the dancer is expanding her/his arms(& her mass and her arms mass...etc). So you will calculate L(t) as a function output of time and you must know both L & w at some instant (maybe before after she moves her arms)simultaneously, this way you will know w(t).

NOOOOOOOO! don't count the number of rotation per second, I have no grudge over counting but it will give an average w over a time of 1 sec, which will be hazardous if w is not constant.
 
  • #3
welcome to pf!

himassb! welcome to pf! :smile:
massb said:
In my experiment … I understand this concept and even somewhat how the calculate it except my angular momentum.

L=Iw since my inertia is changing how do I find the changing w(angular momentum) if I don't know the value of the L(angular momentum) yet. Would I just physically count the number of rotations per second in radians for each time the inertia is changed?

angular momentum is difficult to measure directly (if you don't know the moment of inertia)

the only convenient way i can think of is to transfer all the angular momentum to a "reference" body

what exactly is your experimental set-up?​
 

1. What is the purpose of conducting a Moment of Inertia Experiment?

The purpose of a Moment of Inertia Experiment is to determine the distribution of mass and how it affects the rotational inertia of an object. This information is important in understanding the behavior of objects in motion and can be applied in various fields such as engineering, physics, and mechanics.

2. How is the moment of inertia measured in an experiment?

In an experiment, the moment of inertia can be measured by using a rotating apparatus such as a torsion pendulum or a spinning disk. The object's mass and its distance from the axis of rotation are also taken into account in the calculation of moment of inertia.

3. What factors affect the moment of inertia of an object?

The moment of inertia of an object is affected by its mass, shape, and the distance of its mass from the axis of rotation. Objects with greater mass or mass concentrated further from the axis of rotation will have a larger moment of inertia. Additionally, objects with a larger radius of gyration (i.e. more spread out mass) will also have a larger moment of inertia.

4. How does the moment of inertia differ from the center of mass?

The center of mass of an object is the point at which its entire mass can be considered to be concentrated, and it is used to describe the translational motion of an object. The moment of inertia, on the other hand, is a measure of an object's resistance to rotational motion and takes into account the distribution of mass around the axis of rotation.

5. What are some real-life applications of the moment of inertia?

The concept of moment of inertia is widely used in various fields, such as engineering and physics. It is used in designing structures, such as bridges and buildings, to ensure their stability and resistance to rotational forces. In sports, understanding moment of inertia is crucial in improving performance, such as in figure skating and diving. It is also used in the development of tools and machines, such as flywheels and gyroscopes.

Similar threads

Replies
5
Views
1K
Replies
11
Views
1K
  • Mechanics
Replies
9
Views
4K
Replies
2
Views
2K
  • Mechanics
Replies
1
Views
1K
Replies
1
Views
4K
Replies
34
Views
5K
Replies
10
Views
1K
Replies
3
Views
737
Back
Top