7. Three point charges lie along the x axis as shown in Figure. The positive cha

Question

7. Three point charges lie along the x axis as shown in Figure. The positive charge q1-15.0 C is at x-2.00 m, the positive charge q:" 6.00 C is at the origin, and the net force acting on q is zero. What is the x coordinate of qy? 2.00 m 2.00- 91 8. Two point charges -25 uC and +50 uC, are separated by a distance of 100 cm. What is the electric field (magnitude and direction) at a point halfway between the two charges? 9. In an optics experiment, a discharge tube is filled with singly ionized argon atoms, each having a mass of 6.64 x 1026 kg. If the electric field inside the tube is 7500 N/C, find the acceleration of each argon ion. 10. A pair of parallel plates are charged with uniform charge densities of 35 pC/m2 and +35 pC/m2, and the distance between the plates is 2.3 mm. If a free electron is released at rest from the negative plate, find (a) its speed when it reaches the positive plate and (b) the time it takes to travel across the 2.3-mm gap

Explanation / Answer

7) F13 = F23

kq2 / x^2 = kq1 / (2-x)^2

6 / x^2 = 15 / (2-x)^2

6(2 - x)^2 = 15x^2

6(4 + x^2 - 4x) = 15x^2

9x^2 + 24x - 24 = 0

x = -24 + sqrt(24^2 + 4*24*9) / 18

= 0.77 m

8) EF due to -25 uC = kq / r^2

= 9*10^9*25*10^-6 / 0.5^2

= 9*10^5 N/C ( towards the charge)

EF due to 50 uC = 9*10^9*50*10^-6 / 0.5^2

= 18*10^5 (towards the negative charge)

Net EF = 10^5(18 + 9) = 2.7*10^6 N/C (towards the negative charge)

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