The motion of a space shuttle breaking through Earths atmosphere can be explained by physical principals discovered over three hundred years ago by Sir Isaac Newton. He developed three laws of motion which many examples are demonstrated throughout this movie. Sir Isaac Newtons three laws of motion are .
I. An object in motion tends to stay in motion, an object at rest tends to stay at rest, unless the object is acted upon by an outside force.
II. The acceleration of an object acted on by an unbalanced force is inversely proportional to mass. | Fnet = Mass ~ Acceleration |.
III. Every action has an equal or opposite reaction.
Some examples of Newtons laws are when they reach the speed for orbit around the earth, gas molecules pushing the shuttle forward in space, and the force needed to escape Earths atmosphere. .
When the space shuttle reached the critical speed for orbit around the earth, the astronauts of Apollo 13 shut down the engines. They did this because they know of Newtons First Law that if an object that is in motion will stay in motion. When the engines are shut down, the space shuttle will no longer be accelerating. If there is no acceleration, then there is constant speed as there will be no force acting against the motion in space. When a centripetal force is applied from Earths gravity the space shuttle will continue forever in Earths orbit. That will be true until an unbalanced force acts upon it.
Newtons Second Law states that the acceleration of an object is inversely proportional to its mass. | Fnet = Mass ~ Acceleration | explains that the mass of the object multiplied by the acceleration gives the force measured in newtons. The force of gravity equals the normal force. For the space shuttle to leave Earths gravity it will need tremendous acceleration. The force needed to do this must be greater than the force of gravity pulling down on the shuttle, thus a greater normal force.