Two charges of 1C and 2C are positioned on a line at points 2 and 2, respectively. What is the net force on a charge of 1C at 1?

1 Answer
Dec 30, 2015

F3=1.91010N

Explanation:

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Consider the figure. Let the charges 1C,2C and 1C be denoted by q1,q2 and q3 respectively.
Let the positions at which charges are placed be in the units of meters.

Let r13be the distance between the charges q1andq3.
From figure
r13=1(2)=1+2=3m

Let r23be the distance between the charges q2andq3.
From figure
r23=21=1m

Let F13 be the force due to charge q1 on the charge q3
F13=kq1q3r213=9109(1)(1)32=1109N
This force is repulsive and is towards charge q2.

Let F23 be the force due to charge q2 on the charge q3
F23=kq2q3r223=9109(2)(1)12=18109N
This force is attractive and is towards charge q2.

The total force or net force on charge q3 is the sum of above two forces.
Since the above two forces F13 and F23 are in same direction therefore they can be added directly.
Let F3 be the total force on the charge q3.
F3=F13+F23=1109+18109=19109=1.91010N
F3=1.91010N
Since F13andF23 are toward the charge q2 therefore the force F3 is also toward the charge q2.