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to the rod. 38 mmh A 3.0 C point charge is placed in an external uniform electri

ID: 1573045 • Letter: T

Question

to the rod. 38 mmh A 3.0 C point charge is placed in an external uniform electric field that has a magnitude of 1.6 × 104 N/C, At what distance from the charge is the net electric field zero? 39. ssm A tiny ball (mass 0.012 kg) carries a charge of-18 C, what electric field (magnitude and direction) is needed to cause the ball to float above the ground? 40, GO A proton and an electron are moving due east in a constant elec- tric field that also points due east. The electric field has a magnitude of 8.0 × 104 NC. Determine the magnitude of the acceleration of the proton and the electron.

Explanation / Answer

38.

given

q = 3*10-6 C

E = 1.6*104 N/C

k*q2/r2 = 1.6*104

9*109 *(3*10-6)2 / r2 = 1.6*104

r2 = 5.062*10-6

r = 2.25*10-3 m

r = 2.25 mm

40.

m*a = q*E

a = q*E/m

for the proton

ap= 1.6*10-19 *8*104 / 1.67*10-27

ap = 7.66*1012 m/s2

for the electron

ae = 1.6*10-19 * 8*104/9.10*10-31

ae = 1.40*1016 m/s2