A small 12.4 g plastic ball is tied to a very light 28.3 c m string that is atta

Question

A small 12.4g plastic ball is tied to a very light 28.3cmstring that is attached to the vertical wall of a room. (See the figure (Figure 1) .) A uniform horizontal electric field exists in this room. When the ball has been given an excess charge of -1.40?C , you observe that it remains suspended, with the string making an angle of 17.4? with the wall.

Find the magnitude of the electric field in the room.

to the right to the left A small 12.4g plastic ball is tied to a very light 28.3cmstring that is attached to the vertical wall of a room. (See the figure (Figure 1) .) A uniform horizontal electric field exists in this room. When the ball has been given an excess charge of -1.40?C , you observe that it remains suspended, with the string making an angle of 17.4? with the wall. Find the magnitude of the electric field in the room.

Explanation / Answer

F = E*q
then the body is in equlibrium then

?y =0 mg = T cos?
(or) T = mg/ cos? ----------(1)

?x=0 F = T sin?

Eq = Tsin?

thenthe magnitude of electric field is
E = Tsin? /q
=mg tan? /q from equation (1)
= ( 0.0124Kg)(9.8m/s^2)*tan 17.40 /(1.40*10^-6C )
= 2.72x10^4 N/C

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