Question

Firefox File Edit View History Bookmarks Tools Window Halo Chapter 22 PHY 211 i Feb 1 108 AM Consider the two sman, equal-mass, charged spheres shown in the ngure. The top spheres suspended from the celing b. tring. adhS inrpeof n·n ,c m bottom sphere has a charge of a2--58.0 nC, and is directly below the top sphere. Assume d 2.00 cm and m 7.60g 92 (a) Calculate the tension (in N) in the string Draw a free-body diagram of the upper sphere. Note that there are essentially three forces acting on the sphere: you can neglect the gravitational force from the lower sphere because its magnitude is so small Write Newton's second law in the vertical direction and solve for the tension T.N (b) İf the string can withstand a maxim um tenson of 0.180 N. what is the smatest vated an have b.se the ing been, cae oe ne second law to the top sphere, and solve your equation for the distance d. Set -0.180 N. cm Need Help? oGk Subt Answer Save Progress 8 4 5 6 2 3

Answer 1

Force acting on the top sphere

1. its own weight mg - down

2. weight of the hanging sphere mg -down

3. electrostatic force between the two charges = k q1 q2 /d² - down

4. Tension in the string T - up

for equilibrium

T = kq1q2/d² +2mg

= 9.0E+9 *27.9E-9*58.9E-9 /0.02² + 2*7.6E-3*10 ( we take g=10)

= 0.189N

max. tension T= 0.180 N

smaller the d larger the force and tension T increases

0.180 <= 9.0E+9 *27.9E-9*58.9E-9 /d² + 2*7.6E-3*10

d = 2.3 cm