Answer:
height above the fixed charge is 8.571 cm
Explanation:
given data
mass m = 0.050 g = 5 × [tex]10^{-5}[/tex] kg
charge bead q1 = 20 nC = 20 × [tex]10^{-9}[/tex] C
charge base q2 = 20 nC = 20× [tex]10^{-9}[/tex] C
to find out
what height above the fixed charge does the bead rest
solution
we know that when charge at rest then downward gravitational force is balance by electrostatic force so
[tex]mg = k\frac{q1q2}{r^2}[/tex] .............1
here k is 9 × [tex]10^{9}[/tex] Nm²/C² and g = 9.8 m/s² and r is height of bread
put here all value in equation 1
[tex]5*10^{-5}*9.8 = 9*10^{9} \frac{20*10^{-9}*20*10^{-9}}{(r^2}[/tex]
r² = 7.3469 × [tex]10^{-3}[/tex]
r = 0.08571 m = 8.571 cm
so height above the fixed charge is 8.571 cm
