In which state of matter has the least kinetic energy

Solid state

Explanation:

Kinetic energy is the energy associated with the motion, in a solid particles are close together so they don't move much, inside a solid the electrons of the atoms vibrate constantly but they are fixed in their position because of how the structure of the atoms behaves in this state. In conclusion, the solid-state has some kinetic energy associated with the vibration of electrons but this energy is much smaller than in liquids or gases.

probably not if net force is zero

the components of a vector are the parts of the vectors that are to each other.

b perpendicular