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hw Figure (a) shows charged particles 1 and 2 that are fixed in place on an x ax

ID: 2275466 • Letter: H

Question

hw

Figure (a) shows charged particles 1 and 2 that are fixed in place on an x axis. Particle 1 has a charge with a magnitude of lq1l = 22e. Particle 3 of charge q3 = +22e is initially on the x axis near particle 2.Then particle 3 is gradually moved in the positive direction of the x axis. As a result, the magnitude of the net electrostatic force on particle 2 due to particles 1 and 3 changes. Figure (b) gives the x component of that net force as a function of the position x of particle 3. The scale of the x axis is set by xs= 1.40 m. The plot has an asymptote of F2,net = 3.937 times 10-25 N as x infinty. As a multiple of e and including the sign, what is the charge q2of particle 2?

Explanation / Answer

According to the given plot in (b), as x tends to infinity, force on particle 2 = 3.937*10^-25

We can deduce that as x tends to infinity, force on particle 2 due to particle 3 is 0

Thus, the total force on 2 is only due to particle 1 which is kq1q2/r^2

= 9*10^9*22*1.6*10^-19*q2/r^2

For determining r, we look at the graph again. We can observe that at x = 2.8 m, force on q2 = 0. Thus force by q1 = force by q3. Since q1 = q3, we can assume that q1 is also situated 2.8 m away from q2

Thus r = 2.8 m

Force = 4.04*10^-9*q2 = 3.937*10^-25

=> q2 = 0.974*10^-16 C