Aristotle quotes are numerous and cover excellence, education, love, happiness, life, etc. He was a great philosopher and observer of life. He was a thinker but not the doer that Galileo would be. The difference in their approach to questions was like night and day.

Galileo was at the forefront of the scientific revolution when we finally put the sun at the center of our solar system and we turned to experiment, logic, and reason to attempt to answer questions about ourselves and the universe we inhabit.

1. A force is needed to maintain motion: Aristotle

An object in motion stays in motion until acted upon by a force: Galileo

2. Heavy objects fall faster than light objects: Aristotle

All objects fall at the same rate: Galileo

You are familiar with the idea of speed as most people drive or understand the concept of speed. Speed is a ratio of distance and time. Ratios have a numerator and a denominator and both have units. Speed is distance (miles, meters, kilometers, etc) over time (seconds, minutes, hours, etc). Velocity is the same except it has direction. Quantities that have magnitude and direction are called vectors.

Acceleration is another ratio but it is a ratio (velocity-m/s) divided by time again so that there are squared time units in the denominator.

Free fall represents motion with only one force acting on it-the force of gravity. The velocity changes by 10m/s (actually 9.81 m/s) every second as the picture above represents.

Mass is the amount of matter in an object. Those particles are the matter. More particles = more matter = more mass. Not all particles have the same mass.

Weight is the force of gravity acting on mass. Forces are measured in newtons (N) and so is weight.

Inertia is the resistance to a change in motion. The more mass and object has, the more inertia the object has. It will require more force to make a massive object change its motion (changing motion = move = change direction)

The normal or support force that holds on object on a table is equal but opposite in direction to the weight of the object.

When an object is not resting on a table but is being supported by a rope or cable in midair, the tension is like the normal force. Tension is equal but opposite in direction to the weight of the object.

In both of the examples above, an object is at rest (also known as constant velocity) so the forces are in equilibrium.