Download Describing Motion - chapter 1 - St. Thomas the Apostle School

MOTION
Think of a time you went to an
amusement park. Describe three rides
and how they caused you to move.
A reference point is needed to determine
the position of an object.
Motion occurs when an object changes its
position relative to a reference point.
Frame of reference- a coordinate system in
which the position of the object is measured. The
x-axis and y-axis are drawn so that they
intersect the reference point
Distance- An important part of describing the
motion of an object to describe how far it has
moved.
Displacement- The distance and direction of an
objects change in position from the starting
point.
HOW DO DISTANCE AND
DISPLACEMENT DIFFER?
Distance describes how far an object has moved;
Displacement includes distance and direction of
an object’s change in position from its starting
point.
SPEED
- The distance an object travels per unit of time.
Calculating speedSpeed ( In meters/seconds)= Distance/time
s=d/t
1. If a motorcyclist travels 20 km/h
to a friends home 5 km away,
how long will the trip take?
2. A car traveling a constant speed covers a distance of
750m in 25s. What’s the cars speed?
Typical speeds
• Airplane- 548 mph
• Car- 60 mph
• Person walking- 2.9mph
• Motion with a constant speed- If an item
travels in a speed that does not slow down,
nor speed up. For example: A car traveling on
a highway
• Changing speed: intervals of speeding up and
slowing down. For example-A car at a stop
sign.
• Average speed- The total distance traveled
divided by the total time of travel.
• Instantaneous speed- the speed at a given
point in time
• Changing instantaneous speed- the speed is
different at every point in time.
Distance –time graph
Graphing motion
Time is always plotted on the horizontal ais of
the graph. Distance traveled is plotted on the
vertical axis of the graph.
• The slope of a line plotted on a distance- time
graph is the speed.
Graphing motion
Velocity
• - includes the speed of an object and the
direction of its motion.
• * For an object to have constant velocity, speed
and direction must not be changing.
HOW ARE SPEED AND VELOCITY
DIFFERENT?
Velocity includes direction; speed does not
How can you tell if you are accelerating while
riding in a vehicle?
Acceleration- is a measure of the
change in velocity during a period of
time.
When a car slows down, is it accelerating?
speed time graphs
Motion of the Earth’s crust
• Geological evidence has shown that the
Earth’s continents have moved slowly over
time.
• Pangea began to separate into smaller pieces .
The continents are still moving today!
• The Earth’s crust moves over putty like interior