Inclined plane with friction, find kinetic energy.

AI Thread Summary
The discussion revolves around solving a physics problem involving two blocks on an inclined plane with friction. The user seeks verification of their calculations for the variation of kinetic energy when block m1 ascends 20 meters. Key equations include Newton's second law and kinetic energy formulas, with specific attention to the effects of friction. Corrections were suggested regarding the acceleration calculation, particularly the inclusion of gravitational force and friction components. Overall, the user received confirmation that their reasoning and formula application were correct despite minor calculation errors.
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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