A proton is projected in the positive x direction into a region of uniform electric field E = (a) Determine the acceleration of the proton. m/s magnitude direction -X (b) Determine the initial speed of the proton. m/s magnitude direction +X (c) Determine the time interval over which the proton comes to rest. S (-5.70 105) N/C at t = 0. The proton travels 7.80 cm as it comes to rest.