Problem 6: Two positive charges are placed on the x-axis as shown in the diagram

Question

Problem 6: Two positive charges are placed on the x-axis as shown in the diagram below. They are both at rest and have a mass of 2.0g Which exerts a larger force: the force that charge two exerts on charge 1 or the force that charge 2 exerts on charge 1? Explain. A. (-9 m. 0 m) (+16 m,0m) How much electric potential energy does the system have? ls this energy positive or negative? B. while q, remains How much work would be required to move the q, fixed? Does this correspond to an increase or decrease in electric potential energy? c. 6nC charge to point 0, D. If charge 2 is allowed to move (while charge 1 still remains fixed in place), at what speed would charge q, be moving as it passes through its original position( 9 cm)? E. How fast will charge 2 be moving by the time I gets very far away?

Explanation / Answer

A.

Both the forces will be equal.

As we know that the force between two point charges is ,

F=Kq1q2/r2

And we can deduce from the formulae as well, they will be same.

B.

Electric potential energy is ,

U=Kq1q2/r

So,

U=9*109*8*6*10-18/25

U=1.728*10-8J

It is positive

C.

Work done will be equal to change in the potential energy of the system

U at new position,

U=9*109*8*6*10-18/16

=2.7*10-8J

So change in potential energy,

=(2.7-1.728)*10-8J

=0.972*10-8J

therefore increase in potetnital energy

D.

Whatever will be the change in potential energy is, it will be in the form of kinetic energy ,

So

0.5mv2=0.972*10-8J

v=3.1177*10-3m/s

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