A small 2.0 g mass is suspended from a massless thread. An unknown charge \"q\"

Question

A small 2.0 g mass is suspended from a massless thread. An unknown charge "q" is placed on the mass. When a horizontal electric field having magnitude 2000 N/C pointing left to right is applied, the mass moves to the position shown and then comes to a stop, with the thread making a 40* angle with the vertical.

a) Is the charge q positive or negative? (DO NOT NEED HELP WITH THIS ONE)

b) How many forces are acting on the charged 2.0 g mass? What are they? (DO NOT NEED HELP WITH THIS ONE)

c) Calculate the magnitude of the charge "q" present on the mass. Give your answer in microcoulombs. Hint: Draw a Free Body Diagram for the charged mass. (DO NEED HELP WITH THIS ONE)

Explanation / Answer

depending upon your coemments, I am giving answer to part c:

Let the tension in thread = T

T cos 40 = mg

T sin 40 = qE

tan 40 = qE/ mg

0.839 = q ( 2000) / (2 x 10^-3 x 9.8)

q=8.22 micro C apprx

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