If all of the forces acting on an object balance so that the net force is zero, then
(a) the object must be at rest
(b) the object’s speed will decrease
(c) the object will follow a parabolic trajectory
(d) the object’s direction of motion can change, but its speed cannot
(e) none of the above

Auniform electric field exists in the region between two oppositely charged plane parallel plates separated by a distance of 1.60 cm . a proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate in a time interval of 3.20×10-6 s. 1-find the magnitude of the electric field. use 1.60×10-19c for the magnitude of the charge on an electron and 1.67×10-27kg for the mass of a proton 2-find the speed of the proton when it strikes the negatively charged plate