Chapter 2 Newton's First Law of Motion - Inertia Newton's First Law of Motion - Inertia

1.ARISTOTLE ON MOTION Aristotle attempted to understand motion by classification Two Classes: –Natural and Violent Aristotle attempted to understand motion by classification Two Classes: –Natural and Violent

Natural Motion Natural motion depended on nature of the object. Examples: A rocks falls because it is heavy, a cloud floats because it’s light The falling speed of an object was supposed to be proportional to its weight. Natural motion depended on nature of the object. Examples: A rocks falls because it is heavy, a cloud floats because it’s light The falling speed of an object was supposed to be proportional to its weight.

Natural Motion Natural motion could be circular (perfect objects in perfect motion with no end).

Violent Motion Pushing or pulling forces imposed motion. Some motions were difficult to understand. Example: the flight of an arrow There was a normal state of rest except for celestial bodies. Pushing or pulling forces imposed motion. Some motions were difficult to understand. Example: the flight of an arrow There was a normal state of rest except for celestial bodies.

Aristotle Aristotle was unquestioned for 2000 years. Most thought that the Earth was the center of everything for it was in its normal state. No one could imagine a force that could move it. Aristotle was unquestioned for 2000 years. Most thought that the Earth was the center of everything for it was in its normal state. No one could imagine a force that could move it.

2.COPERNICUS AND THE MOVING EARTH Sun was center, not earth. (Heliocentric) He was hesitant to publish because he didn't really believe it either. De Revolutionibus reached him on the day he died, May 24, Sun was center, not earth. (Heliocentric) He was hesitant to publish because he didn't really believe it either. De Revolutionibus reached him on the day he died, May 24, 1543.

17 th Century scientist who supported Copernicus. He refuted many of Aristotle's ideas. Worked on falling object problem - used experiment. 17 th Century scientist who supported Copernicus. He refuted many of Aristotle's ideas. Worked on falling object problem - used experiment. 3.GALILEO AND THE LEANING TOWER

4.GALILEO'S INCLINED PLANES Knocked down Aristotle's push or pull ideas. Rest was not a natural state. The concept of inertia was introduced. Galileo is sometimes referred to as the “Father of Experimentation.” Knocked down Aristotle's push or pull ideas. Rest was not a natural state. The concept of inertia was introduced. Galileo is sometimes referred to as the “Father of Experimentation.”

Galileo He tested with planes. Demo - Ball and Incline PlaneDemo - Ball and Incline Plane The change in speed depended on the slope of the incline. He tested with planes. Demo - Ball and Incline PlaneDemo - Ball and Incline Plane The change in speed depended on the slope of the incline.

5. NEWTON’S FIRST LAW OF MOTION Newton finished the overthrow of Aristotelian ideas. Law 1 (Law of Inertia) An object at rest will stay at rest and an object in motion will stay in motion unless acted upon by an outside force. Newton finished the overthrow of Aristotelian ideas. Law 1 (Law of Inertia) An object at rest will stay at rest and an object in motion will stay in motion unless acted upon by an outside force.

Demonstrations Demo - Weight and String Demo - Card, Cup, and Coin Demo - Swinging Rocks Demo - Coins on Elbow Demo - Table Setting Demo - Bottle, Hoop, and Chalk Demo – Lead Brick and Hammer Demo - Weight and String Demo - Card, Cup, and Coin Demo - Swinging Rocks Demo - Coins on Elbow Demo - Table Setting Demo - Bottle, Hoop, and Chalk Demo – Lead Brick and Hammer

10 N 6.NET FORCE A force or a combination of forces produces changes in motion (accelerations). 10 N m = 20 N m 10 N m = 0 N m 10 N m 20 N = m

Examples of Mechanical Equilibrium: Normal up Weight down Scales pushing up Tree pulling up Normal Friction 7.THE EQUILIBRIUM RULE Computer setting on a table Weighing yourself on a set of scales Hanging from a tree Car parked on an incline Computer setting on a table Weighing yourself on a set of scales Hanging from a tree Car parked on an incline

The Equilibrium Rule

Scales pushing up Weight down 8.SUPPORT FORCE In the first example of mechanical equilibrium the table supplied a force upward that was called the normal force. It is a support force. Consider the second example of mechanical equilibrium. The scales supply a support force on the man. In the first example of mechanical equilibrium the table supplied a force upward that was called the normal force. It is a support force. Consider the second example of mechanical equilibrium. The scales supply a support force on the man. Normal up Weight down

9. EQUILIBRIUM OF MOVING THINGS Equilibrium is a state of no change. If an object moves in a straight line with no change in speed, it is in equilibrium. Equilibrium is a state of no change. If an object moves in a straight line with no change in speed, it is in equilibrium. Examples: Driving at constant velocity Force from road Air Resistance Normal up Weight down Terminal velocity in parachuting Weight down Air resistance

10. THE MOVING EARTH It is hard to detect the motion of the earth because we are moving with it. Early science could not predict large enough forces to move the earth. Can Hewitt’s bird drop down and catch the worm if the Earth moves at 30 km/s? Demo - Cart and Ball Launcher Video – Snowmobile and Flare It is hard to detect the motion of the earth because we are moving with it. Early science could not predict large enough forces to move the earth. Can Hewitt’s bird drop down and catch the worm if the Earth moves at 30 km/s? Demo - Cart and Ball Launcher Video – Snowmobile and Flare