Electrostatics and infinately charged plate question driving me nuts

In summary, An electron is released from rest 2.0 cm from an infinite charged plane. It accelerates toward the plane and collides with a speed of 1.0x10^7m/s. Using the equations v=d/t, d=0.5at^2, E=n/2*8.85x10^-12, F=ma=Eq, the surface charge density of the plane can be calculated to be 2.52×10−7 C/m^2. Additional kinematic relationships such as Vf^2=V0^2 + 2ad can also be used to find the acceleration and average velocity.
  • #1
ursulan
10
0

Homework Statement


An electron is released from rest 2.0 cm from an infinite charged plane. It accelerates toward the plane and collides with a speed of 1.0x10^7m/s. What is the surface charge density of the plane?The answer is 2.52×10−7 C/m^2 !


Homework Equations


v=d/t, d=0.5at^2, E=n/2*8.85x10^-12, F=ma=Eq


The Attempt at a Solution


I don't know what to do with the velocity. I tried relating it to energy but got stuck.
 
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  • #2
ursulan said:
I don't know what to do with the velocity.
Use that and the distance to find the electron's acceleration.
 
  • #3
using v=d/t t is 2E-9
using a=v/t a is 5E15
E=ma/q E=28469
E=n/(2 epsilon not).. n=5.03E-7

which is 2 times too big, but isn't E=n/(2 epsilon not) the correct equation, with the 2?
 
  • #4
ursulan said:
using v=d/t t is 2E-9
That equation applies for constant velocity, not accelerated motion. But you can use it if you replace v (the final velocity) with the average velocity. What's the average velocity?

You can also make use of additional kinematic relationships.
 
  • #5
ahh so I guess you mean Vf^2=V0^2 + 2ad because that works haha

Thanks!
 
  • #6
That's the one. :wink:
 

1. What is electrostatics?

Electrostatics is the study of stationary electric charges and their interactions with each other and with electric fields.

2. How does an infinitely charged plate work?

An infinitely charged plate means that the charge on the plate is spread out over an infinitely large surface. This creates a uniform electric field around the plate, with the strength of the field decreasing as you move further away from the plate.

3. What is the relationship between electric field and distance from an infinitely charged plate?

The strength of the electric field decreases as you move further away from an infinitely charged plate. This relationship follows an inverse square law, meaning that the electric field strength is inversely proportional to the distance squared.

4. How is electric potential related to an infinitely charged plate?

The electric potential near an infinitely charged plate is constant, meaning that it has the same value at all points near the plate. This is because the electric field is uniform and has the same strength at all points near the plate.

5. What is the significance of an infinitely charged plate in electrostatics?

An infinitely charged plate is a simplified model used in electrostatics to understand the behavior of electric fields and potential. It helps to visualize and analyze the effects of a uniform electric field on charged particles and provides a basis for more complex calculations and applications in electrostatics.

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