Motion Scientists

Aristotle

• Aristotle:• Greece- 335-325 B.C.• What he said people

believed because he was well educated

Aristotle

• Gravity: heavier objects fall faster than light objects • Experiment: Dropped rock and feather at the same

time, the rock hit the ground first• Motion: objects only move if you push/pull them,

and objects only stop if you stop pushing/pulling them (*did not mention outside forces)

• His ideas lasted for about 2000 years = BIG DEAL! That is a LONG time to be considered correct

Galileo

• Italy- early 1600s• “Renaissance Man” – good at many things• Challenged Aristotle’s ideas

Galileo

• Gravity: objects fall at the same rate regardless of mass

• Experiment: dropped a 3 pound cannon ball and a 5 pound cannon ball from the same height (Tower of Pisa) at the same time, and both hit the ground at the same time

• This experiment shows the opposite of Aristotle’s idea

Galileo

• Motion: objects in motion stay moving until an “invisible force” or another object stops them (“invisible forces” friction!)

• NOTICE: this concept is like Newton’s 1st Law• Galileo is credited with idea of “inertia”• Inertia is the resistance to a change in motion

Aristotle & Galileo

• NOTICE: At this point, neither person has mentioned air resistance!

Newton

• England, late 1600s• Was Galileo’s student,

so used Galileo’s ideas and added to them

• Combined Aristotle and Galileo’s ideas

Newton

• Gravity:– Objects fall at the same rate regardless of mass, in the

absence of air resistance• Motion: 3 Laws1. Law of inertia (object in motion stays in motion,

object at rest stays at rest, until outside force)2. Force = mass x acceleration

**need more force to move a larger mass!

3. For every action, there is an equal and opposite reaction