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~christina~
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Homework Statement
A light spring of constant k= 90.0N/m is attatched to a table vertically.
A 2.00g balloon is filled with helium (d= 0.180kg/m^3) to a volume of 5.00m^3 and is then connected to the spring, causing the spring to stretch as shown. Determine the distance L when the balloon is in equillibrium.
http://img222.imageshack.us/img222/9371/93040485ij0.th.jpg
Homework Equations
I think...not sure ...
[tex]K_i + U_i = K_f + U_f [/tex]
[tex] K_i + (U_g + Ui_s) = K_f + (U_g + Ui_s) [/tex]
B= \rho Vg
(B= buoyant force of air)
I know that if it is in equillibrium it would be:
[tex] \sum Fy= 0 [/tex]
The Attempt at a Solution
I'm not sure how to put all this that I compiled together...good grief
first of all I think that
the equation would sort of look like this:
[tex]K_i + U_i = K_f + U_f [/tex]
[tex] K_i + (U_gi + Ui_s) = K_f + (U_g + Ui_s)[/tex]
BUT AM I Supposed to use this equation? or...F= kx
and how do I incorperate the buoyant force into that?
[I do know that the weight of the balloon will be a force downward and the spring will be a downward pulling force and the buoyant force is facing up but other than that...well I tried.]
And now I'm officially confused and lost here...
![Cry :cry: :cry:](/styles/physicsforums/xenforo/smilies/cry.png)
(I need help setting up the equation)
help please
Thanks
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