Rotational Motion: Rotational vs. translational kinetic energy

[adenine135]

In an inertia experiment using equipment very similar to the link below, I determined the following:

Trial with two 100 g masses near the ends of the rotating apparatus (larger moment arm):
- Final translational kinetic energy: 5.73 * 10^(-4) J
- Final rotational kinetic energy: 0.638 J

Trial with two 100 g masses closer in on the rotating apparatus (smaller moment arm):
- Final translational kinetic energy: 1.27 * 10^(-3) J
- Final rotational kinetic energy: 0.638 J

The final rotational kinetic energy is much larger than the final translational kinetic energy. Why is that the case?

http://www.usdidactic.com/images/produktbilder/04061000/Datenblatt/04061000 2.pdf

 

[Drakkith]

Is translational energy the movement of an object other than rotating? IE left/right, up/down, ETC?

 

[adenine135]

Translational kinetic energy is the kinetic energy associated with rectilinear motion, equal to 1/2*m*v^2.

 

[Drakkith]

Translational kinetic energy is the kinetic energy associated with rectilinear motion, equal to 1/2*m*v^2.

Looks to me like the you have very little translational energy because its all rotational energy. The small amount of translational energy is possible from the center of mass wobbling about?

Got my info from here: https://www.physicsforums.com/showthread.php?t=177052

 

[PJC01]

This is a very interesting observation from your inertia experiment. It is important to note that rotational and translational kinetic energy are two different types of energy that are associated with different types of motion. Translational kinetic energy is the energy associated with the linear motion of an object, while rotational kinetic energy is the energy associated with the rotational motion of an object.

In your experiment, you have observed that the final rotational kinetic energy is much larger than the final translational kinetic energy. This is because rotational motion involves a larger moment arm, which is the distance between the axis of rotation and the point where force is applied. In the first trial, where the masses were placed near the ends of the rotating apparatus, the moment arm was larger, resulting in a larger rotational kinetic energy. In the second trial, where the masses were placed closer to the axis of rotation, the moment arm was smaller, resulting in a smaller rotational kinetic energy.

It is also important to note that rotational kinetic energy depends on the mass and the square of the angular velocity, while translational kinetic energy depends on the mass and the square of the linear velocity. This means that even if the angular velocity remains the same in both trials, the larger moment arm in the first trial results in a larger rotational kinetic energy. This highlights the importance of considering both the moment arm and angular velocity when studying rotational motion.

In conclusion, your experiment has shown that rotational kinetic energy is larger than translational kinetic energy due to the larger moment arm involved in rotational motion. This reinforces the concept that different types of motion have different types of energy associated with them.