An electron with known speed and distance from a proton moving away?

[zoomrocket88]

Homework Statement

Suppose that an electron is set down 10e-10 m away from a proton that is "pinned down" so that the proton cannot move. The electron has a velocity V0= 1.6e6 m/s pointing away from the proton, along the line between the proton and the electron. What is the force on this electron? Explain its motion in terms of energy conservation. How far away will it get from the proton? Where will it end up?

Homework Equations

Not sure

The Attempt at a Solution

I am stumped at how to go about this. I know that you should turn the changing kinetic energy into potential energy, and that eventually the electron will stop and come back to the proton if the attractive force is grater than the initial velocity of the electron, but I have no idea how to go about it.

 

[turin]

You need Coulomb's Law. You need the kinetic energy equation. Force and velocity are not comparable quantities.

 

[zoomrocket88]

Alright so I can find the values for kinetic energy and the force from those equations, but how do I relate the two to find out how far the electron will go?

I have 1.16e-18 J and 2.30e-8 C so far...

 

[zoomrocket88]

I suppose you could divide the two and get the Electric Potential but I don't think that would help...

 

[zoomrocket88]

I found an equation that states that an electron will escape the pull of a proton if:
V=sqrt (2kQe/mr) but I can't tell if Qe is one value or two. Any help?

 

[turin]

Please state Coulomb's Law for us. Please give your math in "complete sentences" (use equations, not just numbers or expressions).

 

[ideasrule]

While you're at it, also state the equation for electric potential energy.

 

[zoomrocket88]

Coulomb's law states that the force of attraction or repulsion between two charged particles is directly proportional to the product of the charges and inversely proportional to the distance between them.

 

[zoomrocket88]

The equation for potential energy is PE= kQq/r

 

[turin]

Coulomb's law states that the force of attraction or repulsion between two charged particles is directly proportional to the product of the charges and inversely proportional to the distance between them.

Excellent. And, these days, we know the constant of proportionality, so when you look up Coulomb's law in a textbook, for instance, you will see this constant, and the textbook will tell you it's value. Use this to answer the first question (What is the force).