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A charge particle of mass 1 gram is suspended through a silk thread of length 40cm in a horizontal electric field 4*10^4 NC-1.if the particle stays at a

distance of 224 cm from the wall.find the charge.
reply as fast as possible...need help badly


Three forces act on mass here
1. Tension in the thread (along the thread)
2. mg weight of the mass particle (downward)
3. Electric force F=QE due to horizontal field
Let the angle between thread and vertical be  \alpha   
Then use sine law
T= \frac{mg}{sin(90+ \alpha )}= \frac{QE}{sin(180- \alpha )}
m=10^{-3} Kg
QE=mg(tan( \alpha ))
Q= \frac{mg(tan( \alpha ))}{E}
the length of thread is 40 cm
But the distance from the vertical cannot be 224 cm please check ur question
any way this would help u
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