# How to find when the voltage gets zeroed

1. Jun 7, 2012

### Distance

1. The problem statement, all variables and given/known data
Basically, I was given this graph: http://i48.tinypic.com/qrdabs.png
In addition I was asked to find out what's the work of the net force between x=0m and x=6m.

2. Relevant equations

I'm not sure but I believe this one(?): WƩF=ΔEk

3. The attempt at a solution

Well...as I said I was trying to find it with the equation of WƩF=ΔEk but it doesn't seem to be relevant...
I was also trying to use the graph, yet I have no idea how to reach the answer with it.

2. Jun 8, 2012

### Staff: Mentor

Hi Distance! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

The title of your thread is something about voltage. I see nothing pertaining to voltage in the thread. You have a graph of Force vs. distance and are attempting to determine Work Done.

There is an equation: Work = F ⋅ s
for F constant, and s is distance.

Otherwise, for changing F, use Work = F ⋅ ds
Did you make this up? I presume Ek is kinetic energy?

Last edited by a moderator: May 6, 2017
3. Jun 8, 2012

### Distance

I wrote voltage instead of velocity...No idea why. And yes, Ek stands for kinetic energy. Can you/anybody else please help with my question(when does the velocity get zeroed?). Thanks

4. Jun 8, 2012

### SammyS

Staff Emeritus
Re: How to find when the VELOCITY gets zeroed?

Is that a graph of the net Force vs. displacement?

If it's not net Force, then you can't do the problem.

First: Answer "what's the work of the net force between x=0m and x=6m."

Then work on the title question ... although you can't answer "when", you can answer "where".

5. Jun 8, 2012

### Staff: Mentor

Is the mass of the body known?

6. Jun 9, 2012

### Distance

Yes, it is a graph of the net Force vs. displacement.
Sorry for not mentioning it, but I already found the work of the net Force(48J).
How can I answer where(I think my teacher was mistaken)?

No, there's another question to find the mass of the body and it's after this question so it's not relevant.

7. Jun 9, 2012

### Staff: Mentor

Hint: If we assume the body starts from rest at x=0, then from x=0 to x=10 it has been continuously acted on by an accelerating force, so its speed reaches a maximum at x=10.

8. Jun 9, 2012

### Distance

So all I can say is that the speed will be zeroed at x>10m?

9. Jun 9, 2012

### Staff: Mentor

There is a precise numerical answer.

After 10m, the force undergoes a change....

10. Jun 9, 2012

### Distance

Alright I reached to the right answer(x=18m).
Thank you very much!

Last edited: Jun 9, 2012