A box of mass 96 kg is at rest on a horizontal frictionless surface. A constant horizontal force F then acts on the box, and accelerates it to the right. It is observed that it takes the box 4.3 seconds to travel 58 meters. What is the magnitude of the force?

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?