- #1

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F = (k q1 q2) / r^2

Q1 and Q2 are the same so

F = (k q^2) / r^2

q = sqrt[ (F r^2) / k ]

where r is the distance between the balls (taken as point charges)

Using cosine rule, a^2 = b^2 + c^2 - 2 b c cosA

where a = r

b and c = 0.48m

A = 10 degrees

a = sqrt( 2 * 0.48^2 - 2 * 0.48^2 * cos 10)

r = 0.0083669513m

F = force on each ball

F = mass * acceleration due to gravity * sin (5 degrees)

F = 0.0025kg * 9.81 * sin(5)

F = 2.14 * 10^-3

k = electrostatic constant = 9 * 10^9 N m^2 C^-2

so q = sqrt[ (F r^2) / k ]

q = sqrt[ (2.14 * 10^-3 x 0.0083669513^2) / 9 * 10^9]

q = sqrt( 1.664584116E-17)

q = 4.1E-9 C

I have tried almost everything, but I keep getting the wrong answer. Where am I going wrong? Am I even on the right track? Any help would be greatly appreciated.