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at each corner of a rhobus , made of rods, each with a length of B, there are electric charges of "Q" and "q" so that each q charge is opposite a q charge and each Q charge opposite a Q charge. what does the ratio of Q/q need to be so that the angle (alpha) is
a)90 degrees
b)60 degrees
c)45 degrees
(take the tension of the rods into account)
i started up by taking one of the corners and analyzing the forces on it, since the shape is static, Ftotal=0.
i took the top Q charge and said, what are the forces acting on it,
the Coulumb force F(Q-Q) which pushes it upwards
the Coulumb force F(Q-q) which (depends on the charge)
the tension os the rods T
my problem is that i do not know which of the charges are negative(if any) or positive, so i cannot decide on the directions of the forces, the only one i do know is F(Q-Q) since Q must repell Q,
diagram below
diagram below
http://picasaweb.google.com/devanlevin/DropBox?authkey=Gv1sRgCL_4l4PpvP_YsQE#5311131135994735922 [Broken]
a)90 degrees
b)60 degrees
c)45 degrees
(take the tension of the rods into account)
i started up by taking one of the corners and analyzing the forces on it, since the shape is static, Ftotal=0.
i took the top Q charge and said, what are the forces acting on it,
the Coulumb force F(Q-Q) which pushes it upwards
the Coulumb force F(Q-q) which (depends on the charge)
the tension os the rods T
my problem is that i do not know which of the charges are negative(if any) or positive, so i cannot decide on the directions of the forces, the only one i do know is F(Q-Q) since Q must repell Q,
diagram below
diagram below
http://picasaweb.google.com/devanlevin/DropBox?authkey=Gv1sRgCL_4l4PpvP_YsQE#5311131135994735922 [Broken]
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