Law Conservation of Energy: Starting off a solution for 11b

  • Thread starter Jigga
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Homework Statement


upload_2018-6-9_17-43-24.png


Homework Equations


ΔEsystem + ΔEsurroundings =0

The Attempt at a Solution


I have solved 11a and got 5m/s.
I can do 11b just by just jumping to Ek = Fs (from the work kinetic energy theorem), but I would like to do it formally from first principles using the Law of Conservation of Energy.
I would then like to make use of
ΔEsystem + ΔEsurroundings =0
and then make use of ΔEsystem = ΔU + ΔEk + ΔEp
and then make use of ΔU = W + Q
and then introduce W = Fs
then solve for F.
However I am not sure where to put the system boundary so this is solvable. Then the question of the pluses and minuses.


Many thanks
 

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Answers and Replies

  • #2
CWatters
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Depending on where you draw the system boundary the heat generated by friction will either remain within the system boundary (part of Delta E system) or cross the boundary (part of Delta E Surroundings) either way it's solvable.
 
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