- #1
David112234
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Homework Statement
What is the distance Δy between the two points that you observe? Assume that the plates have length d, and use e and m for the charge and the mass of the electrons, respectively.
Express your answer in terms of e, m, d, v0, L, and E0.
Homework Equations
kinematics equations
F=qE=ma
The Attempt at a Solution
Split the problem into 2 sections, the first being with acceleration due to the electric field,
t1 = when particle lease electric field
t2 = when particle hits screen
so at t1 a distance d
d = v0t
Δy1 = ½at2
t values are unknown so I eliminate t
t=d/v0
and
qE0=ma
q=e
(eE0)/m = a
Δy1 = ½((eE0)/m) (d/v0)2
now for the x and y components of velocity at this point
using the equation
v=v0+at
vy = 0 + ((eE0)/m)(d/v0
vx has not changed so = v0
Now is have the height at d and both components of velocity, I can use kinematics to find the particles motion from d to L using these values (at d) as the initial points.
Δy2 = Δy1 + vy(t)
this t value will be
L= v0 t
t= L/v0
plugging it all in
= ½((eE0)/m) (d/v0)2 +
(eE0/m)d/v0*L/v0
This is not the correct answer for Δy2
once I know Δy2 I can find Δy = Δy2 + Δy1
But I can not find my mistake in finding Δy2
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