Three rigid rods are joined to form an equilateral triangle ABC of side 1m.Three particles carrying charge 20 micro Coloumb of charge are placed at the vertices.The whole system is at rest in an inertial frame.What is the magnitude of the net force on charged particle A?
a) 0
b)3.6 N
c)3.6 * root 3 N
d)7.2 N

Question

Three rigid rods are joined to form an equilateral triangle ABC of side 1m.Three particles carrying charge 20 micro Coloumb of charge are placed at the vertices.The whole system is at rest in an inertial frame.What is the magnitude of the net force on charged particle A? 
a) 0
b)3.6 N
c)3.6 * root 3 N
d)7.2 N

jamesj · Answer

Ok, what's the formula for the Coloumb's law, the gives us the magnitude of the force between two point charges?

anonymous · Answer

(k *q1*q2)/r^2 ?

jamesj · Answer

Yes.  Use that the find the force acting on any one charge.  Note that the direction of the force is always along the axis between them.  Then remember that two positive charges repel, two negative charges repel, and one positive and one negative charge attract.

anonymous · Answer

okay will try, but in this question, they havent mentioned the sign of the charges.

anonymous · Answer

and neither do i have the value of k

jamesj · Answer

Yes they have.  20 microC.  Not -20 microC.  And k is a well established constant that your class or text book will give you.  Its value is always the same. and to two significant figures it is
$$ k = 9.0 \times 10^9 \ N . m^2/C^2 $$

anonymous · Answer

oh sorry i forgot the value of k..:) thanks for reminding

anonymous · Answer

let me draw a pic - |dw:1333828839292:dw|