Physics question!?

Two 3.4 g point charges on 1.0-m-long threads repel each other after being equally charged, as shown in the figure.(Figure 1) Assume that θ = 26 ∘.

What is the charge q?

?2018-09-09T21:03:06Z

Favorite Answer

for each thread, vertical force
Fy = 0.0034kg * 9.8m/s² = 0.03332 N
so the horizontal component is such that
tanΘ = Fx / Fy, or
Fx = Fy * tanΘ = 0.03332N * tan26º = 0.01625 N

the inter-charge distance
d = 2LsinΘ = 2 * 1m * sin26º = 0.877 m

electrostatic force
F = kq² / d²
so
q² = Fd² / k = 0.01625N * * (0.877m)² / 8.99e9N·m²/C² = 1.39e-12 C²
so
q = 1.2e-6 C = 1.2 µC
either both negative or both positive
to two significant digits

Hope this helps!