Describing and Measuring Motion Energy and Motion Table of Contents 8.3 Describing and Measuring Motion Nicolaus Copernicus

Vocabulary 8.3 Reference Point- A place or object used for comparison to determine if an object is in motion. International System of Units (SI): A system of measurements based on multiples of ten and on established measures of mass, length, and time. Distance: The length of the path between two points. Motion- the state in which one object’s distance from another is changing. (if position is changes when compared to another object)

My Planet Diary pg. 302 Nicolaus Copernicus Why should anyone think that Earth moves around the sun? After all, on a clear day you can see the sun move across the sky. But Polish astronomer Nicolaus Copernicus realized that an object revolving around you from left to right looks the same as an object standing still while you rotate from right to left. In 1543, Copernicus published On the Revolution of the Heavenly Spheres, a book based on his 30-year study of the solar system.

Interactive Art Pearson Interactive video clip

When is an Object in Motion? Pg. 302 An object is in motion if it changes position relative to a reference point. A reference point is a place or object used for comparison to determine if something is in motion. How do you know when an object is in motion? To determine motion for an object moving on or near Earth’s surface, a reference point that is fixed to Earth, such as a building or tree, is usually used.

Did you Know?? Pg. 303 Because of Earth’s spin, the stars appear to move in circular arcs across the night sky. Only the North Star remains in a fixed position. Historically, sailors have used the North Star to help them navigate.

Measuring Distance pg. 305 How do you know something is moving? How do you know the distance from one place to another? (Miami to Orlando?) To describe/explain motion completely, you need to use units of measurements. Scientists use a system of measurement called the International System of Units. In French, this system’s name is Système International, so it is commonly referred to by the abbreviation SI. What is Distance? Distance is the length of the path between two points. SI unit for length= meter (m). Example: The distance from the floor to a doorknob is about 1 meter.

Measuring Distance pg. 305 Scientists use other units to measure distances much smaller or much larger than a meter. For smaller distances =centimeters and millimeters are used. The prefix centi- means “one hundredth.” A centimeter is one hundredth of a meter, so there are 100 centimeters in a meter. The prefix milli- means “one thousandth,” so there are 1,000 millimeters in a meter. To measure distances much larger than a meter, kilometers are used. The prefix kilo- means “one thousand,” so there are 1,000 meters in a kilometer.