- #1
Medeiros
Homework Statement
Two small spheres of 15 g each are suspended from a common point by threads of length 35 cm. Each thread makes an angle with the vertical of 20 degrees. Each sphere carries the same charge. Find the magnitude of this charge.
(The correct answer is: 0.58 μC)
Homework Equations
1) F= k|q1| |q2| / r2
2) SOH CAH TOA
3) F=ma
The Attempt at a Solution
I drew a picture of the 2 strings hanging from the same point and labelled the angles.
Knowing that F(g)=max on Y axis and = 0 on X axis,
I thought I could get the force of gravity on the two particles by
angle x g x mass
sin(20) x 9.81 x 0.015 = 0.05033...N
(I also did this another way by finding a vector from how much of the string on the Y axis as missing, and doing a ratio between that and the length of the string, which took a long time and turned out to be sin(20) anyway)
From there, I plugged that force in Eq.1:
q2 = Fr2 / k
so q = 0.56625 μC
Although it is close, I didn't round off anything to get that answer, and my answer still doesn't round off to the correct one.
I was just wondering if
1. Did I get the force the wrong way?
2. Is there another way to do this?
Thank you in advance
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