10.1 MEASURING MOTION
I CAN…
 explain how motion is dependent of the observers frame of reference.
 explain motion in terms of position, displacement, velocity, and acceleration which are all
vector properties.
 draw and interpret motion diagrams to represent position and velocity of an object.
 calculate the displacement or change in position of an object.
 distinguish between distance and displacement, (speed and velocity)
 describe velocity as a vector property that represents the rate at which position changes
 calculate average velocity, which may be positive or negative.
 recognize the difference between average speed and average velocity.
 recognize the difference between instantaneous speed and average speed.
 recognize constant velocity on a motion diagram.
MOTION
 An object’s change in position relative to a reference point.
 You must observe the object in relation to another object that stays in place:
stationary object , reference point, or reference frame.
 Ex: Comparing a hot air balloons movement to a mountain in the background. (n,s,e,w)
VECTORS
 a physical quantity that includes both size and direction.
DISTANCE V. DISPLACEMENT
 Distance: the length of the path an
object travels
 Displacement: is the distance and
direction of an object’s final position
from its initial position.
 Differences:
 Distance can be a straight line, but
doesn’t have to be.
 Displacement must be a straight line.
(Displacement may be shorter)
 Displacement must include a particular
direction.
SPEED
 Speed: the distance traveled divided by the time interval during which the motion
occurred.
 Equation: s=d/t
 Units: SI unit for speed is meters per second (m/s).
 Will also be seen as km/h or mi/h. Why?
 Constant Speed: object covers equal distances in equal amounts of time.
 Ex: race car travels a distance of 96 meters every second.
Time (s)
Distance (m)
0
0
1
96
2
192
3
288
DISTANCE-TIME GRAPH
 X axis=independent variable, y
axis=dependent variable
 These lines are representing constant
speed.
 Which line represents the fastest
moving object?
 How do you know?
 How would an object at rest be
represented?
AVERAGE SPEED, INSTANTANEOUS SPEED,
VELOCITY
 Total distance/Total Time=average
speed
 Ex: a wheel chair racer finishes a 132 m
race in 18s.
 v=d/t=132m/18s=__________
 7.3m/s
 Instantaneous Speed: measured in an
infinitely small time interval.
 Ex: car speedometer
 Velocity: the speed of an object in a
particular direction
PRACTICE CALCULATING VELOCITY
 Find the velocity in m/s of a baseball thrown 38 m from third base to first base in
1.7 seconds
 22m/s toward first base
 Metal stakes are sometimes placed in glaciers to help measure a glacier’s
movement. For several days in 1936, Alaska’s Black Rapids glacier surged as
swiftly as 89 meters per day down the valley. Find the glacier’s velocity in m/s.