Inclined plane with friction, find kinetic energy.

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Homework Help Overview

The problem involves two blocks connected by a rope over a massless pulley, with one block on an inclined plane. The objective is to find the variation of kinetic energy as one block moves up the incline, considering the angle of the incline and the coefficient of kinetic friction.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to solve the problem using Newton's second law and kinetic energy equations, while seeking confirmation on their reasoning and calculations. Some participants question specific components of the equations used, such as the inclusion of gravitational forces and friction.

Discussion Status

Participants are actively engaging in checking the original poster's calculations and reasoning. There is a mix of feedback, with some affirming the approach while others point out potential errors in the setup. The discussion reflects a collaborative effort to clarify the problem without reaching a definitive conclusion.

Contextual Notes

The original poster is working under exam conditions and is seeking validation of their approach and calculations, indicating a focus on understanding rather than simply obtaining an answer.

dttah
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I need someone to double check it, because this was an exam given by my teacher and I am trying to solve it, but I do not have any results so I would like to know if I did it correctly or not. Thank you!

Homework Statement



Two blocks m1 = 50kg and m2= 100kg are attached to a rope as shown in figure. Pulley is massless. The angle of the inclined plane is pi/6 and the coefficient of kinetic friction is 0.250. Find the variation of kinetic energy if the body m1 goes up 20meters.

Homework Equations


F = ma
kinetic energy = 1/2 mv^2
kinetic friction = mu*normal force.

The Attempt at a Solution


See attachment
or: http://i40.tinypic.com/6hklm8.jpg for better quality.

Thanks for any help.
 

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Welcome to PF! Thanks for taking time to show your whole solution so clearly.

Over on the right side, where you first have "a =", it appears you are missing a "-m₂g" in the numerator. Also, the "μ*m₁*cos(30)" should have a factor of g as well. I end up with a negative acceleration (m₂ goes down) of about 4.
 
Aw, how could I fall in such a stupid typos mistakes ! :(.
Thanks a lot, that's appreciated. Forgetting about the "numbers" is the reasoning correct ( I mean the use of the formulas) or is there anything wrong? Thanks a lot!
 
Yes, it all looks good! Nice use of variables right up to the calculation stage.
 
Alright! Thanks a lot, I am grateful and I appreciate your help. Thanks again :)
 
Most welcome.
 

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