posted by Alex .
Consider a disk of radius 10 cm and positive surface charge density +3.7 mC/m2. A particle of charge -4.5 mC and mass 75. mg accelerates under the effects of the electric field caused by the disk, from a point at a perpendicular distance from the center of the disk.
The final speed of the particle is 1.0 m/s and the work done on the particle by the electric field is -3.0 mJ.
How fast and in what direction was the particle originally moving?