Question

A small charged bead has a mass of 1.9 g . it is held in a uniform electric field e⃗ = (200,000 n/c, up). when the bead is released, it accelerates upward with an acceleration of 15 m/s2 .

Answer 1

As we know that when charge is released in electric field

It will have two forces on it

1. electrostatic force

2. gravitational force

now if the ball will accelerate upwards so we can say

net upward force = mass * acceleration

$qE - mg = ma$

$q*200000 - 1.9 * 10^{-3}* 9.8 = 1.9 * 10^{-3}* 15$

now we can find charge q on it by above equation

$q = 0.2356 * 10^{-6} C$

So above is the charge on the particle