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Need help with # 3, #8 and #4 iPad 6:53 AM * 75% - webassign.net Master it 3. 0/

ID: 1881589 • Letter: N

Question

Need help with # 3, #8 and #4

iPad 6:53 AM * 75% - webassign.net Master it 3. 0/1.25 points | Previous Answers My Notes Ask Your Teache Two small metallic spheres, each of mass m = 0.182 g, are suspended as pendulums by light strings of length L as shown in the figure below. The spheres are given the same electric charge of 6.9 nC, and they come to equilibrium when each string is at an angle of = 5.10° with the vertical. How long are the strings? 139 Your response differs from the correct answer by more than 10%. Double check your calculations. m LII Need Help? Read It Submit Answer Save Progress Practice Another Version 4. 1.25/1.25 points | Previous Answers My NotesAsk Your Teache Three point charges lie along a circle of radius r at angles of 30°, 150°, and 270° as shown in the figure below. Find a symbolic expression for the resultant electric field at the center of the circle. (Use the following as necessary: ke, q, and r.)

Explanation / Answer

Considering equilibrium of forces along x axis

F = T sin ......(1)

Considering forces along vertical
T cos - mg = 0
T cos = mg ......(2)

Dividing (1) by (2)

Tan = F / mg

F = mg tan

From figure  
  
a = L sin (3)

Force between two charges is

F = k q 2 / r 2  

mg tan = ( 9*109)(7.3*10-9 C)2 / ( 2a)2  

0.182*10^-3* 9.8 *tan (5.1) = ( 9*10^9)(6.9*10-9)2 / ( 2a)2  

a = 0.02594

Putting in (3)

L sin = 0.02594

L = 0.292 m
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