# Chapter 9 sec. 1 Describing Motion

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Chapter 9 sec. 1 Describing Motion
MOTION AND ENERGY Chapter 9 sec. 1 Describing Motion

What is physics? Physics is the study of matter, energy, motion, and forces, and how they interact.

Has anyone ever sat in a train or flown somewhere?
Were you moving? Answer- Yes and No

Motion Motion- When the distance from another object is changing.
Reference Point- a starting place or object used to determine if something is in motion. As you sit still in your desk, are you in motion relative to your desk? What is the reference point? Reference point- THE DESK *An object is in motion if it changes position relative to a reference point. * (if the starting point gets closer or further or up or down, or even left or right; then there is motion.)

?? ?? ?? ?? What is a reference point?-
A place or object used for comparison to determine if something is in motion. Why is it good to choose something that is stationary as a reference point? If you choose something that is moving you make think you are moving when you are not, or that you are moving faster than you really are. Ex: use a fast little kid outside running around as a reference point, what can you conclude?

Relative Motion Open books to page 340.
Relative motion- whether or not an object is in motion depends on the reference point. Skydivers and the plane. Relativity to the sun- are we moving relative to the sun?

Distance and Displacement
Distance- The total length of a path between two points. (Yellow line) Displacement- the length and direction of a straight line between starting and ending points. (red line)

Distance and Displacement
Vector- an arrow that represents the magnitude or size and direction of something moving. An arrow has a size, its length, and a direction, the direction in which it is pointing. So, to draw a vector we need just to draw an arrow:

Distance and Displacement
B The arrow represents the size, magnitude and speed of a moving object. It also represents direction. N, E, S, W. Which arrow represents a greater magnitude? Which arrow represents a slower speed? What is the direction of both arrows? A

Walk about it. With a partner
Take out a penny or some type of change, and a small sheet of paper (used) Place the penny on the ground Now have a meter stick and with your paper walk somewhere else in the class use the piece of paper to represent your ending point. Now find the distance Now find the displacement. On a sheet of paper give me the vector for the small walk you had.

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