keep getting something wrong....not sure why....can i get some help?

Question

anonymous · Answer

calculating k (constant) from info i have.  mass of pith ball is .05 grams.  distance between balls is 5.5 cm.  angle of separation is 4 degrees.  |dw:1421663895396:dw|

anonymous · Answer

computer shows charge on pith balls to be 3.357*10^-9

i have mg=Ftensiony and Felec=Ftensionx.  Ftensionx=Tcos(theta), Ftensiony=Tsin(theta).  

5*10^-5(9.8)=Tsin(4)  

T=0.00702N

0.00702cos(4)=Felec=.007N

Felec=k(q^2)/r^2 == 0.007=k(3.357*10^-9^2)/.055^2=1.88*10^12.  k isn't near that.  i'm off too much.  what did i do wrong?

anonymous · Answer

|dw:1421687095426:dw|

anonymous · Answer

take your time to analyze the problem,don't just take numbers :P

anonymous · Answer

well that doesn't make sense cause i did it the same way for parts 1 and 2.  x was cos theta and y was sin theta.  and x is Fcoulomb.  so not sure what i did wrong.

anonymous · Answer

5*10^-5(9.8)=Tsin(4)  that would be cos4 !

perl · Answer

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