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 2.6 g mass from it. This stretches the spring to a length of 5.4 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 4.7 cm .

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

I have already tried 2.63*10^-8 C.

Explanation / Answer

given

unstretched length is 4.0 cm

spring to the ceiling and hang a 2.6 g mass from it.

the spring to a length of 5.4 cm .

This stretches the spring to a length of 4.7 cm

charge = ?

using

F = - k . x

2.6 X 980 = - k X 1.4

k = - 2.6 X 980 / 1.4

k = - 1820 g/s2

agian taking F = - k. x

= 1820 X ( 4.7 - 4 )

= 1820 X 0.7

F = 1274 dynes

using the force equation is

F = 9 X 109 X q1 X q2 / r2     

q1 = q2

1274 = 9 X 109 X q2 / 4.72

q2 = 1274 X 4.7 X 4.7 / 9 X 109

q2 = 3.1296 X 10-6

q = 1.76 X 10-3 C

the magnitude of the charge on each bead q = 1.76 X 10-3 C

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