1.) Try out the following home experiment: take two similar strips of tape and s
ID: 1329563 • Letter: 1
Question
1.) Try out the following home experiment: take two similar strips of tape and stick them onto a smooth surface (like a smooth wooden table). You expect that when you pull the strips off of the surface, each will be charged and that the amount of charge on each is similar. Based on this, you expect that if you hold the strips from the top ends and slowly bring them close, trying to keep them parallel to each other, they will repel and push apart. Come up with a simple model which will allow you to roughly estimate the magnitude of charge on either strip from observing the angle that the strips make with the vertical direction and the distance between the centers of the strips. Estimate the charge magnitude on one of the strips to within an order of magnitude (i.e. a factor of 10) if you were to observe that the strip made an angle of 10 degrees with the vertical direction and that the centers of the strips were about 1 cm apart. Assume that the strip of tape has a mass of about 0.1 grams.
Explanation / Answer
In Horizontal,
Tsin@ = Fe = electric force
Tsin@ = kq1q2 / d^2 = 9 x 10^9 x q^2 / 0.01^2
Tsin@ = 9 x 10^13 q^2 ... (i)
In vertical,
Tcos@ = mg = 0.1 x 10^-3 x 9.81
Tcos@ = 9.81 x 10^-4 ... (ii)
(i) / (ii) =>
tan@ = 9.17 x 10^16 x q^2
q^2 = tan10 / 9.17 x 10^16
q = 1.39 x 10^-9 C
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