The earth rotates on its axis every and revolves around the sun every
a. day . . year
b. month . . day
c. year . . month
d. year . . day

Quantum mechanics applies to subatomic, atomic, nanometer-size, and micrometer-size systems. nanometer, micrometer, and kilometer-size systems. atomic, nanometer-size, and micrometer-size systems. subatomic, atomic, and nanometer-size systems.

Is a volume of space that is empty of matter.

How to know which equation of motion to use where?explain