Principle of Conversation Of Energy question

AI Thread Summary
The discussion focuses on calculating the speed of a 3kg object connected to a 5kg object via a pulley, using the principle of conservation of energy. The 5kg object is released from a height of 4m, and the conservation of energy equation is applied to determine the speed of the 3kg object as the 5kg object reaches the ground. The initial calculations yield a speed of 4.43 m/s for the 3kg object. Additionally, it is noted that the acceleration of the 5kg object is not equal to g, prompting the need for a free body diagram to accurately assess the system's dynamics. The discussion emphasizes the importance of understanding both energy conservation and forces acting on the objects for accurate calculations.
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Homework Statement



2 objects are connected by a light string passing over a light frictionless pulley. The 5kg object is released from rest. Using the principle of conservation of energy, (a) determine the speed of the 3kg object just as the 5kg object hits the ground


The picture shows the 3kg object at rest connected by a string to a pulley vertically...and the 5kg object hangin from a string from the pulley with 4m height between the ground and the 5kg object.




Homework Equations



4.43m/s is answer to a



The Attempt at a Solution



.5mv^2 + g(mf-mi)y=.5(5)v^2 + (-9.8)(2)(4)===>

2.5v^2= 78.4
v=5.6m/s
 
Last edited:
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When the 5kg object is released from rest, its acceleration in not g. Calculate its acceleration by drawing free body diagram. 3 kg moves up with the same acceleration. Then apply the conservation of energy for 3 kg mass to calculate its velocity.
 
Draw An F.b.d.
 

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