Posted by Jordie on Tuesday, April 27, 2010 at 1:02pm.
an electron is launched at a 30 degree angle with respect to the horizontal and a speed of 3.0*10^6 m/s from the positive plate of the parallel plate capacitor. THe plats of the capacitor are oriented horizontally. The electron lands 5 cm away from the point of release.
a) what is the electric field strength inside the capacitor?
would i use E=(1/4*pi*Eo)(q/r^2)
where q=e and r=5cm
b) what is the minimum separation between the plates?
very confused. any help would be great

Physics  drwls, Tuesday, April 27, 2010 at 1:33pm
a) No don't use that formula. It is the formula for the field strength at distance r from a point source. Your field comes from parallel plates.
This is like a ballistics problem with gravity negligible. The downward acceleration "a" is provided by the field, and equals E*e.
The horizontal range is [V^2/a]sin (2A) = 0.05 m where A is the launch angle of 30 degrees. You may recall that formula from problems in ballistic trajectories. It is easy to derive.
Use that equation to solve for the acceleration a, and then use a = e*E to solve for E.
(b) The plates must be separated by enough distance D to prevent the electrons from hitting the upper plate; otherwise the trajectory is disrupted. That means
(V sin A)^2/2 < a*D
That means the vertical rise distance,
[V sin A/2]*(VsinA/a)
is less than the plate separation, D
Answer This Question
Related Questions
 College physics  Two 2.4 cm diameter disks spaced 1.5 mm apart form a parallel...
 physics  The plates of a parallel plate capacitor are separated by a distance ...
 Physics  An electron traveling at 7.00 x 10^6 m/s enters and passes through a ...
 Physics  An electron is released from rest at the negative plate of a parallel ...
 physics  An electron is released from rest at the negative plate of a parallel ...
 Physics. Speed of electron...  An electron is released from rest at the ...
 Physics  An electron is released from rest at the negative plate of a parallel ...
 Physics #48  An electron is released from rest at the negative plate of a ...
 Physics  The figure shows an electron entering a parallelplate capacitor with ...
 Physics  An electron traveling at 7.00 x 10^6 m/s enters and passes through a ...
More Related Questions