Physics Failure (HELP!)

[Ozzdog]

Hi.

I need to have a set of online questions finished by tomorrow, and this is one of them... (attached).

It should be so damn easy, I know how to do this! The stupid computer keeps telling my I'm wrong.

Massive +69 rep if you tell what answer you get (reasonable).


I JUST HAVE TO PROVE THE COMPUTER WRONG!

 

[hunterrravyn]

Equations
F=C/V
F=C^2/J
Sub
C/V=C^2/J
arange
J=C^2/(C/V)
replave
J=109^2/(109/78)
solve
J=8502.1 (Doesent Sound Right)
hmmm i dont think i did that the right way...

(Been a while since i've used capacatence equtaions and stuff)

 

[Ozzdog]

*Jeopardy music*

 

[Dave312]

Just off the top of my head:
Ct = 1/C1 + 1/C2
Ct = 29.79mF

Qt = Vt * Ct
Qt = 78 * 29.79 * 10^-3 = 2.32C
Charge Qt is the same across each capacitor
V1 = Qt / C1
V1 = 2.32 / 109*10^-3 = 21.3V

E = 0.5 * C1 * V1^2
E = 0.5 * 109*10^-3 * 21.3^2
E= 24.8J

 

[hunterrravyn]

I believe the above post is closer... *facepalm

 

[Ozzdog]

I believe the above post is closer... *facepalm

This is what I get, exactly...

stupid program made me think I misunderstood all this block lol.

 

[duderock101]

this just went straight over my head, ooh candy