# Proton and an electric field?

1. Jan 13, 2008

### samblue

1. The problem statement, all variables and given/known data

A proton moving to the right along the x-axis at 3.8*10^5m/s, enters a region where the electric field of intensity 5.6*10^4n/c points to the left. How far will the proton move before its speed reaches zero? Describe the subsequent motion in deatail/

2. Relevant equations

dont know whethere to about doing this with force of energy so I really dont know.

3. The attempt at a solution

Im not really sure how to start this, some helpful hints would be appretiated. Thanks.

2. Jan 13, 2008

### mjsd

try $$\vec F= \vec E q$$

E is electric field vector
q is the charge feeling the force

3. Jan 13, 2008

### samblue

Ok but if I work out this force easily enough how is this going to tell me what then time is when its speed gets to zero?

4. Jan 13, 2008

### mjsd

F=ma, once you know a, and if it is constant then that's just kinematic in 1D....

5. Jan 13, 2008

### samblue

thanks

6. Jan 13, 2008

### samblue

Do you have any idea of what i would be expected to write in the "describe the motion" part?

7. Jan 13, 2008

### mjsd

once you know how proton moves under the field, you are done I think....