The ink drops have a radius of 18.0 μm and leave the nozzle and travel toward the paper at a velocity of 20.0 m/s . The drops pass through a charging unit that gives each drop a positive charge q by causing it to lose some electrons. The drops then pass between parallel deflecting plates of length 1.50 cm where there is a uniform vertical electric field with a magnitude of 7.75×104 N/C .
If a drop is to be deflected a distance of 0.350 mm by the time it reaches the end of the deflection plate, what magnitude of charge must be given to the drop? (Assume that the density of the ink drop is 1000kg/m3).
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So I did F = Eq and F = ma to get
a = Eq//m
then I used kinematics and set
1/2at^2 replacing a to get 1/2 * (qE/m) * t^2
therefore q = (2 * d * m) / (E * t2)
but I keep getting
1.6057347713e−13 C which is wrong