Conservation of Angular Momentum Help

AI Thread Summary
The discussion centers on the application of conservation of angular momentum in a physics problem involving a 5 kg ball. The main question raised is why both translational and rotational energy are not considered when calculating the maximum height of the ball. It is clarified that the problem simplifies the scenario by treating the balls as "point masses" and does not provide sufficient information to determine the rotational rate. Additionally, it is noted that without friction or deformation, the bar cannot impart rotation to the ball. The conversation emphasizes the importance of the assumptions made in the problem for solving it correctly.
Speedking96
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Homework Statement


Below is the question:

upload_2014-12-13_12-18-2.png


I only have an issue with the last step of the problem. Why wouldn't you factor in the translational AND rotational energy of the ball and then solve for maximum height?
 
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The translational kinetic energy of the ball is the rotational kinetic energy of a system consisting of the ball alone when using a reference axis such that the ball's radial velocity is zero.
 
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Speedking96 said:
Why wouldn't you factor in the translational AND rotational energy of the ball and then solve for maximum height?

In a real life problem you'd have to do that. In this problem, you have no information that would allow you to calculate a specific number for the rotation rate for the 5 kg ball. You don't know the diameters of the balls. The book expects you to treat them as "point masses".

Without considering friction or the deformation of the objects,, how could the bar impart any rotation to the 5 kg ball?
 
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Alright, I understand. Thank you.
 
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