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Energy Conservation & Potential Energy.. Spring/Friction Problem 
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#1
Mar611, 01:31 PM

P: 9

1. The problem statement, all variables and given/known data
A 0.80kg block is held in place against the spring by a 67N horizontal external force. The external force is removed, and the block is projected with a velocity v1 = 1.2 m/s upon separation from the spring. The block descends a ramp and has a velocity v2 = 1.9 m/s at the bottom. The track is frictionless between points A and B. The block enters a rough section at B, extending to E. The coefficient of kinetic friction is 0.39. The velocity of the block is v3 = 1.4 m/s at C. The block moves on to D, where it stops. In Fig. 7.4, the force constant of the spring is.. 2. Relevant equations K1 +U1 +W other = K2+ U2.. ect .. U2=0.5kx^2 .. K1=(0.5)mv^2 3. The attempt at a solution I've tries solving the problem with the equation above but I really just don't know where to start especially since there are no units of distance given.. Can someone lead me in the right direction please? 


#2
Mar611, 02:08 PM

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P: 26,151

Hi Help1212!
(try using the X^{2} and X_{2} icons just above the Reply box ) I assume you can find kx and kx^{2}/2 ? ok, then k = … ? 


#3
Mar611, 02:57 PM

P: 9

euhh... i'm still a little confused..how do i find k if I don't know x?



#4
Mar611, 03:02 PM

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P: 26,151

Energy Conservation & Potential Energy.. Spring/Friction Problem
x is twice kx^{2}/2 divided by kx



#5
Mar611, 03:31 PM

P: 9

hmm. well when I move around the equation i get k=2[0.5(mv^{2}_{2})/x^{2}
from the assumption that K_{1} + U_{1} = K_{2} + U_{2} Am i going in the right direction?? 


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