Calculating Point Charge from Kinetic Energy and Electric Potential

[peaceandlove]

Homework Statement

A point charge Q resides at the origin. A particle of mass 0.005 kg carries a charge of 2 µC. The particle is released from rest at x=3 m. Its kinetic energy as it passes x=0.5 m is 0.28 J. The Coulomb constance is 8.99x10^9 N*m^2/C^2. Find the charge Q. Answer in units of µC.

Homework Equations

Conservation of energy: PE_f + KE_f = PE_i + KE_i

The Attempt at a Solution

KE_i = 0 (starts from rest)
PE_i = kqQ/xi = kqQ/3
KE_f = .28 j
PE_f = kqQ/.5
kqQ[(1/.5) - (1/3)] = - .28
(8.99 x 10^9)(2)Q[1.66667] = -.28
Q = -9.3437152 x 10^-12 µC

What am I missing or doing wrong?

 

[rl.bhat]

(8.99 x 10^9)(2)Q[1.66667] = -.28
Q = -9.3437152 x 10^-12 µC
The given charge is 2μC

 

[peaceandlove]

Oh wow! Stupid mistake.