# The History of Scientific Thought about Forces & Motion.

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The History of Scientific Thought about Forces & Motion

Aristotle 384 B.C. – 322 B.C.  Greek scientist & philosopher  Made scientific discoveries through careful observations and logical reasoning.

Aristotle believed all motion is linear on the planet Earth: meaning everything moves in a straight line. If I throw this rock, it will travel in a straight line, and also fall in a straight line…. The way Aristotle thought projectiles moved The way projectiles "really" move

When a feather and rock are dropped at the same time, the rock will fall to the ground first. Aristotle believed that the Earth pulls on objects according to their weight.This means that a large heavy object will fall to the ground faster than a large light object Aristotle Reality

Galileo Galilei 1564 - 1642  Astronomer & Physicist  Struggled against the church to have his ideas accepted They locked me up for this?

Falling Objects & gravitational pull  Galileo experimented with ramps and dropping things to find that all objects fall at the same rate. Acceleration due to gravity 9.8 m/s 2 or 9.8 m/s/s

Galileo and Constant Acceleration The inclined plane experiment

Galileo worked out that there was a force acting in the opposite direction to motion and that if this force was decreased (by using oil, grease etc) then the object in motion would move further before stopping. From this Galileo was to formulate his Law of Inertia Unbalanced Forces!

Sir Isaac Newton 1642 - 1727 English mathematician Built on Galileo’s work

1 st Law of Motion An object will keep the same motion unless acted on by an unbalanced force

2 nd Law of Motion  The force of an object depends on the mass of the object multiplied by the acceleration Sometimes, F = ma

3 rd Law of Motion  Every action force has a equal and opposite reaction force.