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August 30th, 2017, 11:13 AM   #1
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mass-spring problem

1. The problem statement:
Suppose at time zero, the bob was drawn upward four units from the equilibrium position, let C=2, K=2, m=1 lbm, initial speed=2 unit/sec find an expression for body's position.

and in the solution it says: y''+6y'+5y=0
my question is: where do the numbers (6) and (5) that are in the above DE come from?
2. Relevant equations
spring equation:
my''+cy'+ky=f(t)
consider f(t) =0

3. The attempt at a solution
stopped at first because of the first step

Last edited by skipjack; August 30th, 2017 at 01:55 PM.
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September 3rd, 2017, 04:45 AM   #2
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If, as you say, my''+ ky'+ Cy= 0 and you are given that C= 2, k= 5, and m= 1 then the equation should be y''+ 5y'+ 2y= 0 with initial condition y(0)= 4, y'(0)= 2.
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