Why Is Kinetic Energy Zero for the 4kg Carriage in This Problem?

AI Thread Summary
The discussion centers on a problem involving kinetic energy (KE) and potential energy (PE) in a system with a 4kg carriage. Participants question why the KE for the carriage is considered zero despite it being in motion. The confusion arises from the equations presented, particularly the line "8.829-11.772+1/2*6*v^2+0=0." It is noted that the carriage's movement is restricted at the moment the links are aligned, limiting its ability to contribute to kinetic energy. The conversation emphasizes the importance of understanding the system's constraints to clarify the energy calculations.
pyroknife
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I attached the problem and the solution.

The book uses V has potential energy and T as KE.

I'm not quite sure how they did this problem. I was following it until the 2nd to last line of equations. where they have "8.829-11.772+1/2*6*v^2+0=0"
Why don't they have the KE for the 4kg carriage? It looks like they said that was 0, but isn't that still moving too?
 

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pyroknife said:
I attached the problem and the solution.

The book uses V has potential energy and T as KE.

I'm not quite sure how they did this problem. I was following it until the 2nd to last line of equations. where they have "8.829-11.772+1/2*6*v^2+0=0"
Why don't they have the KE for the 4kg carriage? It looks like they said that was 0, but isn't that still moving too?

What freedom does it have to move when (at the instant) the links are inline?
 
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