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

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SUMMARY

The discussion centers on the kinetic energy (KE) of a 4kg carriage in a specific physics problem. Participants clarify that the KE for the carriage is considered zero due to its constrained motion at the instant when the links are inline. The equations presented in the problem, specifically "8.829-11.772+1/2*6*v^2+0=0," illustrate the balance of potential energy (PE) and kinetic energy, confirming that the carriage's KE is indeed zero at that moment. This conclusion is based on the principles of mechanics regarding constrained systems.

PREREQUISITES
  • Understanding of basic mechanics principles, particularly kinetic and potential energy.
  • Familiarity with equations of motion and energy conservation.
  • Knowledge of constrained motion in physics.
  • Ability to interpret and analyze physics problems involving multiple bodies.
NEXT STEPS
  • Study the principles of constrained motion in mechanics.
  • Learn about energy conservation in mechanical systems.
  • Explore the concept of potential energy and its relationship to kinetic energy.
  • Review examples of similar physics problems involving multiple bodies and energy calculations.
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the dynamics of constrained systems and energy conservation in mechanics.

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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