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Physics Electrostatics Level: High School

A small 2 g plastic bag is suspended by a 27.4 cm long string in a uniform electric field 1160 N/C as in the figure at ‘click here’ . The ball is in equilibrium when the string makes a(n) 23 degree angle with the vertical . The acceleration of gravity is 9.8 m/s^2 . Use a free body diagram to find the relationship among theta , m g and qE .

1. cos theta = qE/mg

2. sin theta = qE/mg

3. cos theta = mg/qE

4. sin theta = mg /qE

5.tan theta = mg/qE

6.tan theta = qE/ mg

What is the net charge q on the ball ? Answer in units of µC .