Vertical Displacement of Electron (Millikan's Oil Drop)

AI Thread Summary
An electron enters a 150 N/C electric field moving horizontally at 2.50 x 10^6 m/s and follows a parabolic path between two plates. The user calculates the force on the electron and finds the acceleration to be 2.63 x 10^13 m/s². They determine the time taken to travel the length of the plates to be 9.49 x 10^-18 s but struggle to find the vertical displacement. The discussion suggests using kinematics to calculate vertical displacement during the time the electron travels between the plates. The key is to consider the initial vertical speed, which is zero, to accurately determine the vertical distance.
honeybee63
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Homework Statement



An electron moving horizontally at 2.50 x 106 m/s enters a 150 N/C electric field exactly half way between two horizontal parallel plates and follows a parabolic path downwards. Both plates are 14 cm long and spaced 10 cm apart. Determine the vertical displacement of the e- as it travels between the plates.

Homework Equations



E = Fe/q , F=ma , Ep = mgh

The Attempt at a Solution



I found Fe by E/q and got 2.40 x 10-17 J. then I plugged the values into F=ma and found the acceleration to be 2.63 x 1013 m/s2. I then divided the velocity by acceleration and found time to be 9.49 x 10 -18 s. I am now unsure how to find the vertical distance. I used Ep = mgh but got a very large value, so I think that is wrong. Did I make a mistake earlier or should I be using a different equation?
 
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honeybee63 said:
I then divided the velocity by acceleration and found time to be 9.49 x 10 -18 s.
The velocity is horizontal but the acceleration is vertical. Instead, ask how long does it take something moving that fast to cover the needed distance?

Once you have the time, figure out its vertical displacement in that time using kinematics. What is the electron's initial vertical speed?
 

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