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Dynamics got me puzzled :S

  • Thread starter robcowlam
  • Start date
  • #1
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0
HI guys,

Im having some trouble with a dynamics question, I am only looking at a worked example however I can't see where the final answer comes from.
The problem is sample 3/5 on http://www.eng.auburn.edu/~marghitu/MECH2110/Dynamics/D2_1_examples.pdf [Broken]
I follow the working until the line after "which becomes" I cannot see why the integral becomes
F/k [sin(kt)+Uk(cos kt - 1)] - mgt = mv
rather than:

F/k [sin(kt)+Uk(cos kt)] - mgt = mv

Its probably just something small but I cant figure it out,
Can anybody help me out?

Thanks!
 
Last edited by a moderator:

Answers and Replies

  • #2
nvn
Science Advisor
Homework Helper
2,128
32
robcowlam: That is normal calculus (definite integration). Thus, integral[-mu*F*sin(k*t)*dt], integrated from t = 0 to t, is equal to -mu*(F/k)*{-cos(k*t) - [-cos(k*0)]} = -mu*(F/k)*[-cos(k*t) - (-1)] = mu*(F/k)*[cos(k*t) - 1], not mu*(F/k)*cos(k*t).
 
  • #3
9
0
Ah yes I see it now, I wasn't evaluating the integral, thanks for your help.
 

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