Describing Motion
Chapter 1 - Section 1 Notes
P: Identify the properties of objects
that are in motion
Q: How can an object be moving but
not be in motion?
Definitions
• An object is in MOTION if its distance from
another object is changing
• Reference point  a place or object used for
comparison to determine if something is in
motion
• In other words…An object is IN MOTION
when it changes position relative to a
REFERENCE POINT.
Reference Points
• Good Reference Points  = stationary
objects
– (ex: tree, sign, building)
• Bad Reference Points  = any moving
object
– (ex: a moving car, a flying plane)
Types of Motion
•
•
•
•
Straight line
Projectile
Circular
Vibrational
Straight Line Motion
• Occurs when an object moves in a STRAIGHT
LINE
– (ex: a moving car, plane or bicycle)
Projectile Motion
• Occurs when an object is thrown or projected
– Moves in an arc/parabola
• Ex: a shooting cannon ball, arrow from a bow, or
a baseball pitch
Circular Motion
• Occurs when an
object spins/turns
on its axis
– Ex: Earth, a top, a
Ferris wheel
Vibrational Motion
• Occurs when an
object moves back
and forth rapidly
– Ex: Sound waves,
tuning forks, guitar
strings, vocal chords,
etc.
Relative Motion
• Whether or not an object is in motion
depends on the reference point you
choose!
(See PAGE 8 in your textbook)
*Are the skydivers in motion relative to each
other?
*Are they in motion relative to the airplane
from which they jumped?
*Are they in motion relative to the ground?
Consider this…
• Is it possible to be moving,
but NOT be in motion?
LOL _________________________
1) Explain how an object can be moving but not
be in motion. (Use the terms relative motion
and reference point in your explanation.)
2) Compare and contrast the 4 types of motion.
3) List 8 “real life” examples of objects that you
observe in motion today/tonight. (Find at least 2
examples of each type)