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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.