Dumbell problem (conservation of energy)

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SUMMARY

The discussion centers on the physics problem involving a dumbbell leaning against a wall and the conservation of energy principles. The key equation referenced is E = E', indicating the conservation of energy, where the gravitational potential energy is expressed as mgL cos θ. The confusion arises regarding the correct expression for potential energy, with a participant questioning whether it should be mgL sin θ instead. The correct approach involves understanding the geometry of the situation and applying the conservation of energy accurately to determine the angle at which the upper mass begins to fall.

PREREQUISITES
  • Understanding of conservation of energy principles in physics
  • Familiarity with gravitational potential energy equations
  • Basic knowledge of trigonometry, specifically sine and cosine functions
  • Ability to analyze forces acting on inclined objects
NEXT STEPS
  • Review the principles of conservation of energy in mechanical systems
  • Study the derivation of gravitational potential energy formulas
  • Learn about the dynamics of inclined planes and forces on them
  • Explore problem-solving techniques for physics problems involving angles and energy
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Students studying physics, particularly those focusing on mechanics and energy conservation, as well as educators seeking to clarify concepts related to inclined objects and potential energy.

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Homework Statement



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A dumbell is leaned vertically on the wall. After it is deviated with some angle θ, dumbell starts sliding.
Determine the angle between the bar and the horizontal face (floor) when the upper mass starts to fall.

Homework Equations



E = E'

The Attempt at a Solution



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I don't understand how come there is mgL cos θ??
I think the potential should be mg L sin θ, right??

Please help
 
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Right. Do you know how to finish the problem?
 

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