A 22-g metal ball hangs from a string.An electric field of 15,000 N/C,pointing to the right,is then turned on.After the electric field is turned on,the ball hangs at a 25 degree angle away from the vertical.What is the charge on the ball?

Question

Quizplus · Accepted Answer

First, we need to find the force acting on the ball due to the electric field. 
F = Eq = (15000 N/C)(cos 25°)(0.022 kg) = 6.69 N

Next, we need to find the tension in the string. 
T cos 25° = mg    (where T is the tension in the string)
T = mg / cos 25° = (0.022 kg)(9.81 m/s^2) / cos 25° = 0.0251 N

Now, we can find the charge on the ball. 
F = Eq 
q = F / E = 6.69 N / (15000 N/C) = 4.46 x 10^-4 C 
Therefore, the answer is B.

A 22-G Metal Ball Hangs from a String