# physics

posted by on .

ok i have a problem to work on in my new course, and i was wondering what i need to do to tackle it. the question is as follows:

An electron is projected with an initial velocity Vo=10^7m/s into the uniform field between the parallel plates "E". the direction of the field is vertically downward and the field is zero everywhere else except between plates. the electron enters the field at a point midway the plates. if the electron just misses the upper plate as it uses energy from the field, find the magnitude of the field "E"

are these the formulas needed
F = ma = qE
s = ut + 0.5 at^2
v = u + at
v^2 = u^2 + 2as

and what does ( a, u, and s) stand for?

• physics - ,

Eq= force= mass*acceleration

solve for the acceleration upward.

NOTE: the u above is initial velocity, in the direction of deflection, u is zero.
a is acceleration
s is distance. now back to the problem
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I would like to know the measurements of the plates, ie separation, and the length of the plates along the originalpath. Is that given?

• physics - ,

the distance between the two plates is 1cm

and the lengeth of each plate is 2cm

• physics - ,

the distance between the two plates is 1cm

and the lengeth of each plate is 2cm

so how do i get started

• physics - ,

Eq=mass*acceleration
so this is the acceleration toward the plate.

How long is it being accelerated?
lengthplate=V*t solve for time
So then we know that in the vertical acceleration between the plates.
distance moved=1/2 *.001m
but distance moved= 1/2 a t^2
set those equal, solve for a (you know time).

Now Eq=ma you know q, m, a solve for E