ABSTRACT
This chapter examines some of the basic physics. It develops the basics of force, mass and acceleration. Isaac Newton's three laws of motion are discussed and applied to a variety of situations connected with space flight. Newton's laws are clearly visible in the 'simple' situation of being in space. Newton's laws can be used to show that the total amount of momentum in the whole universe never changes. The balloon initially has zero momentum because all the molecules inside it have momentum and at any moment there is as much momentum in one direction as there is in the opposite direction. When a molecule strikes the skin of the balloon it applies a force to the skin. By Newton's third law the skin applies an equal force back and the molecule reverses direction. The products of the reaction have a great deal of energy—their molecules are moving at very high speeds.
