You have a lightweight spring whose unstretched length is 4.0 cm. First, you att

Question

You have a lightweight spring whose unstretched length is 4.0 cm. First, you attach one end of the spring to the ceiling and hang a 3.0 g mass from it. This stretches the spring to a length of 5.3 cm . You then attach two small plastic beads to the opposite ends of the spring, lay the spring on a frictionless table, and give each plastic bead the same charge. This stretches the spring to a length of 4.3 cm .

1)

What is the magnitude of the charge (in nC) on each bead?

Express your answer using two significant figures.

Explanation / Answer

F=kx
mg = -kx
0.003 *9.8 = k (5.3 -4)*0.01
0.0249 = k (1.3*0.01)
k = 2.26 N/m
-----------------on table
stretching = 0.3 cm = 0.003m
F =kx
F = (2.26)(0.003 m) = 6.78 x 10^-3 N

F = K((q1)(q2))/r^2
6.78 x 10^-3= ((9×10^9)(q^2)/(0.043 m)^2

q = 3.73 x 10 ^ -8 and now I need to convert it to nC so = 37.3 nC

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