Quantum physics would most likely be needed to understand the motion of which of the following? a. an atom b. a cell c. a ball d. a galaxy

The correct answer is A.

Quantum physics is the branch of science which deals with the behavior of matter and light on atomic and subatomic level. So, to understand the motion of an atom we would need quantum physics. Motion of a ball and a galaxy can be understood by Newtonian mechanics.

1/0.14nm = 10^10/1.4 a lot

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.