Conservation of Energy and frictionless pulley?

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Homework Help Overview

The problem involves a system of two blocks connected by a string over a frictionless pulley, with one block attached to a spring. The scenario includes concepts of conservation of energy and potential energy related to the height of the blocks and the spring's compression.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of conservation of energy principles, questioning the correct setup of potential and kinetic energy equations. There is a focus on verifying arithmetic and understanding the energy transformations involved.

Discussion Status

Some participants are attempting to clarify the problem setup and the necessary equations, while others are seeking assistance with arithmetic verification. There is an ongoing exploration of different interpretations of the energy conservation equation.

Contextual Notes

Participants express the need for additional information, such as the angle of the incline and the configuration of the spring, which may affect the problem's interpretation. There is also mention of varying answers from different sources, indicating uncertainty in the solution process.

Eukanuba863
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Homework Statement


A 20.0 kg block is connected to a 30.0 kg block by a string that passes over a light, frictionless pulley. The 30.0 kg block is connected to a spring that has negligible mass and a force constant of 240 N/m, as shown in the figure below. The spring is unstretched when the system is as shown in the figure, and the incline is frictionless. The 20.0 kg block is pulled 18.0 cm down the incline (so that the 30.0 kg block is 38.0 cm above the floor) and released from rest. Find the speed of each block when the 30.0 kg block is 20.0 cm above the floor (that is, when the spring is unstretched).



Homework Equations



(K-U)sub(i)=(K-U)sub(f)

The Attempt at a Solution



i've talked with multiple physics teachers on this problem every body got different anwsers...

i'm almost convinced the anwser is 1.1687 m/s^2

Could you help me please?
 
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I need to see the figure. I can't tell the angle of the incline, wether there is one or 2 springs, and in what direction they pull etc.
 
here is the image...

A 20.0 kg block is connected to a 30.0 kg block by a string that passes over a light, frictionless pulley. The 30.0 kg block is connected to a spring that has negligible mass and a force constant of 240 N/m, as shown in the figure below. The spring is unstretched when the system is as shown in the figure, and the incline is frictionless. The 20.0 kg block is pulled 18.0 cm down the incline (so that the 30.0 kg block is 38.0 cm above the floor) and released from rest. Find the speed of each block when the 30.0 kg block is 20.0 cm above the floor (that is, when the spring is unstretched).

p7-45.gif
 
Eukanuba863 said:

Homework Equations



(K-U)sub(i)=(K-U)sub(f)
You want conservation of energy--that's not quite it. Mechanical energy equals KE + PE. (You have multiple forms of PE to track in this problem.)
i'm almost convinced the anwser is 1.1687 m/s^2
Show how you got that.
 
i know the parts just will you check my aritmatic?

it's

(K+U)initial=(K+U)final

and i know all the spring constant parts with .5kx^2, mgh etc.
 
please

could you just check my arithmetic please?
 
Show us your arithmetic so we can check it.
 

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