Any hints or ideas? I know to use a force balance involving tension,

>>16761528
I think that small car should be driving on the road. Try penciling it in.

>>16761554
sounds about right

You were probably under the impression that you would get useful information form these retards, you were wrong. Go to sci.

>>16761528
It has been a while, but you need to figure out the vertical component of the force with relation to the angle.

So drop a trig function in somewhere.

>>16761528
sin(theta)mg=-q

>>16761738
also equilibrium means

sum of forces in ALL directions are 0

the x component of gravity is equal and opposite to the charge force pushing the ball away from the plane

m*g*sin(theta) = qE where E = sigma/epsilon where sigma is the charge density and epsilon is a constant

solve for the charge density

Also don't take my word on the equations, check these up in your textbook

>>16761744
yes but the y direction is not relevant to the question as it only involves the vertical components of tension and gravity; the resulting equation doesn't yield any information that leads to the answer to the question

>>16761757
the x component of the tension*

WAIT I WAS WRONG

Here it is:

Sum of Forces in Y:

Tcos(theta) = mg

Rearranging,

T = mg/cos(theta)

Sum of Forces in X:

Tsin(theta) = qE = q*sigma/epsilon

Subsituting,

mg/cos(theta)*sin(theta) = q*sigma/epsilon

mg*tan(theta) = q*sigma/epsilon

sigma = mg*tan(theta)*epsilon/q

have no fucking clue but that was written on LaTeX so I'm happy about it.