Unit 2 - Motion

What is motion? Understanding motion is important in all areas of science. Do objects start moving on their own or is a force needed to make them move? Do they stop moving on their own or is a force required to stop them? What are the different types of motion?

Motion What type of motion (machine) has done more to change the way cities are built than any other? The elevator!

Aristotle Aristotle was a Greek scientist who lived 2000 years ago. He thought that there were two types of motion: –Natural Motion –Violent Motion

Aristotle’s Natural Motion For all things on the Earth, either straight up or straight down For the celestial objects (Sun, Moon, planets), motion is circular

Natural Motion Aristotle’s “elements” were earth, water, air and fire He thought that all objects had a “natural” place, depending on the element that they belonged to If you throw a rock in the air, it falls because it is made of “earth” Smoke rises because it is made of “air”

Aristotle’s Violent Motion Produced by pushes and pulls (forces). Violent motion is externally caused – it is imposed motion. Motion stops when the pushing/pulling force stops

Galileo A very important contribution that Galileo made to science is that idea that we should try things out to see how they work – experimentation! Galileo developed a quantitative and mathematical approach - measurement.

What do you think? Do heavy object fall to the ground faster than lighter objects? Activity: We are working in groups of 3 to time how long it takes for a light and heavy object to fall the same distance.

Homework According to Aristotle, an object stops because the “force” moving the object stops pushing it. –Do you think this is correct? –Why?

Motion Review