(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Two parallel metallic plates are placed horizontally with a separation of 2.2mm. When the voltage is reduced to zero (so that the plates are neutral), the particle (or sphere) is observed to fall with constant velocity. It is observed to travel 0.85 mm in 8.9s.

A new p.d. V volts is now applied to the plates, which causes the particle to move upwards with a constant velocity of 4 x 10^-5 m/s. You may assume for small velocities like this, the frictional force is proportional to the speed.

Calculate the value of V.

Mass of Particle: 3.5 x 10^-15 kg

Charge of Particle: 6.4 x 10^-19 C

g : 9.81ms^-2

2. Relevant equations

3. The attempt at a solution

KE1= Vq = .5mv^2 0= .5 x 3.5 x 10^-15 x (.00085 / 8.9)^2 = 1.596 x 10^-23J

KE2= Vq = .5mv^2 0= .5 x 3.5 x 10^-15 x (4 x 10^-5)^2 = 2.8 x 10^-24

KEtotal= KE1 + KE2 = 1.876 x 10^-23J = Vq

V = 2.9x10^-5 volts

Isn't this value faaar too small?

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# Homework Help: Motion in Fields (two parallel plates when voltage is applied)

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