Aristotle, Galileo and Newton and Newton’s Laws of Motion

ARISTOTLE 384 BC – 322 BC Ancient Greece One of the first to try to explain the natural world Geocentric view of the universe Ideas based on observations that seemed to be true

GALILEO 1564 – 1642 Italy Perhaps the first true scientist. Rolled and dropped objects to discover the true aspects of motion

NEWTON 1642-1727 England Developed laws for motion and gravity that explain why objects move, and worked with optics

3.1 Aristotle on Motion Natural motion on Earth was thought to be either straight up or straight down. Objects seek their natural resting places: boulders on the ground and smoke high in the air like the clouds. Heavy things fall and very light things rise. Circular motion was natural for the heavens. These motions were considered natural–not caused by forces.

3.3 Galileo on Motion One of Galileo’s great contributions to physics was demolishing the notion that a force is necessary to keep an object moving. In other words, no push or pull would be required to keep it moving once it is set in motion.\ Galileo also stated that this tendency of a moving body to keep moving is natural and that every material object resists changes to its state of motion. The property of a body to resist changes to its state of motion is called inertia. Newton’s Laws of Motion are part of his theory of motion Universally applied Can be used to predict motion Synthesizes previous testing and findings Attempts to explain why

3.1 Aristotle on Motion Objects do not move without a force. Objects in motion always require a force to keep them moving. Objects seek their natural state, which is at rest. Mechanical equilibrium can only be static.

3.1 Galileo and Newton on Motion Objects do not change motion without unbalanced force. Objects in motion do not always require a force to keep them moving. Objects have two “natural” states of motion, at rest (static equilibrium) and moving at a constant speed and direction (dynamic equilibrium). Simply put, things tend to keep on doing what they’re already doing.

3.4 Newton’s Law of Inertia Is a force required to keep an object moving? Newton’s first law, usually called the law of inertia, is a restatement of Galileo’s idea that a force is not needed to keep an object moving. Galileo argued that only when friction is present is a force needed to keep an object moving. Galileo stated that if friction were entirely absent, a ball moving horizontally would move forever at the same speed and in the same direction (at a constant velocity).

3.4 Newton’s Law of Inertia The law of inertia provides a completely different way of viewing motion from the ancients. Objects continue to move by themselves. Forces are needed to overcome any friction that may be present and to set objects in motion initially. Once the object is moving in a force-free environment, it will move in a straight line indefinitely.

In a paragraph, Reflect on the meaning of this cartoon