# Electric potential question

lawandb
I have solved these and got an answer but i have no idea if i have the right work or answer. Can anyone help me with any of these questions? or just tell me what the answer is so i know if i have done it right. Thanx.

1. A particle (charge 7.5x10^(-6)C)is released from rest at a point on the x-axis, x=0.1m. It begins to move due to the presence of a 2.0x10^(-6)C charge which remains fixed at the origin. What is the kinetic energy of the particle at the instant it passes the point x=1.0m?

2. A charge of uniform density (0.80 nC/m) is distributed along the x-axis from the origin to the point x=0.1m. What is the electric potential (relative to zero at infinity) at a point x=0.18m, on the a-axis?

Homework Helper
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What have you done?

lawandb
Here's what i did

1. let *=change in
*K=-*U
*K+*U=0
*U=q(*V)
*V=V2-V1=(k(q1)/r1)-(k(q2)/r2)=(k(7.5nC))/.9-(k (2nC))/.1=1.05x10^5
q(*V)=-7.875x10^-1
*K=7.875x10^-1
--------------------------------------------------------------

2. V=k(.8nC)/.1=72, I'm pretty sure this one is wrong though.