CE Physics:machanics- newton's law and the definition of power

When situation is at rest or in constant acceleration, use newton's first law.
Accelerating, use second law.
Two objects, use third law.
They are some points in the (*) questions.

Power is the rate of change in energy, no matter it is potential energy, kinetic energy,etc
It can be express as P=Fv.
Sometimes differentiation can help solve the problem.