Before the field of physics was officially defined, it was a mixture of

Aregion of space in which a measurable gravitational force is indicated by the force exerted on a test mass is called

Which one of the following research methods can show cause and effect

Two 2.0-cm-diameter disks face each other, 1.0 mm apart. they are charged to ±10 nc. what is the electric field strength between the disks? a proton is shot from the negative disk toward the positive disk. what launch speed must the proton have to just barely reach the positive disk?