What is the displacement of a particle in a constant electric field?

[Melssssss]

Homework Statement

A particle of charge +14.5http://edugen.wileyplus.com/edugen/courses/crs6407/art/qb/qu/c18/lower_mu.gifC and mass 5.09 × 10-5 kg is released from rest in a region where there is a constant electric field of +328 N/C. What is the displacement of the particle after a time of 4.40 × 10-2 s?

http://edugen.wileyplus.com/edugen/courses/crs6407/art/qb/qu/c18/w1706-chap18prob49.gif

Homework Equations

electric force= qE
Elecrtic force= ma

The Attempt at a Solution

I have found the force and the acceleration from above equations. hoe do I use that information to go further.

 

[TSny]

Hint: Is the acceleration constant?

 

[Melssssss]

Hint: Is the acceleration constant?[

I believe so yes.

 

[TSny]

If you know the acceleration and the time, how do you get displacement? You would have studied this early in your coverage of mechanics.

 

[Melssssss]

If you know the acceleration and the time, how do you get displacement? You would have studied this early in your coverage of mechanics.

but the velocity is changing, the picture of it wouldn't load.

 

[TSny]

Yes, the velocity is changing.

Suppose a particle starts at rest and moves with constant acceleration, a, for a time, t. Can you express the final velocity, v_f, in terms of a and t? If you can do that, then you can use the result for v_f to help get the displacement.

 

[Melssssss]

ta + v(initial)

 

[TSny]

ta + v(initial)

OK. For this problem the initial velocity is 0. So, the final velocity is v_f = at. What would be the average velocity during the time t?

 

[Melssssss]

in this case, 4.1128.
so then I would plug all this into this equation
x= vf2-vo2/2a?

 

[TSny]

in this case, 4.1128.
so then I would plug all this into this equation
x= vf2-vo2/2a?

On the formatting toolbar there is an icon for superscripts. So, your equation is x= (vf²-vo²)/(2a). Note the parentheses that I added to make the equation correct according to the rules of "order of operations".

This is one of the well-known formulas for constant acceleration that I was referring to in post #4. This equation will get to the answer if you first calculate vf.

However, if you are familiar with those constant acceleration equations, there is one that would be more convenient for this problem. Do you know of a formula that relates x, vo, a, and t?