Q3.1
A conservation law states that some quantity remains constant. We say the quantity "is conserved." For example, the momentum of an isolated system is conserved.
We use conservation laws by equating the value of the conserved quantity at one point in the problem with its value at a later time. For example, the moment of a two cars before a collision is set equal to the momentum after the collision. Solving this equation can give us information that would be hard to come by using Newton's second law.
Q3.4
The astronaut can throw the tools in the opposite direction of the space station. By conservation of momentum, he will move in the opposite direction from the tools, and therefore toward the space station. This keeps the total momentum of the astronaut plus his tools a constant.
P3.1
P3.6
P3.8
P3.9.
