Question
Please answer the foloowing!!!!
Two small insulating spheres are attached to silk threads and aligned vertically as shown in the figure. These spheres have equal masses of 40 g, and carry charges ql and q2 of equal magnitude 2.0 mu C but opposite sign. The spheres are brought into the positions shown in the figure, with a vertical separation of 15 cm between them. Note that you cannot neglect gravity. (k=1/4piepsilon0=8.99times109 N m2/C2) The tension in the lower thread is closest to (Find answer in Newtons) A +4.00 muC point charge and -4.00 mu C point charge are placed along the x-axis at x = 0.000 cm and x = 40.0 cm, respectively. Where must a third charge, q, be placed along the x-axis so that it does not experience any net electric force due to the other two charges? (answer in m) In the figure, all the charges are point charges and the charge in the middle is Q = -5.4 nC. For what charge q1 will charge q2 be in static equilibrium? (answer in nC)
Explanation / Answer
1. T = F -mg = kq1q2/r^2 - mg = 9 x 10^9 x (2 x 10-6)^2 / 0.15^2 - 0.040 x 9.8
T = 1.208 N
2. F =kq1q2/r^2
Kq1 x 4 x 10-6 / x^2 = kq1 x 4 x10-6 / (x -40)^2
x = 20 cm
so at -20cm or +20cm
3. F = kq1q2/r^2
5.4 x 10-9 x K x q2 / 0.10^2 = Kq1q2 / 0.20^2
q1 = 21.6nC