Unit 4 Lesson 1 Matter in Motion
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Unit 4 Lesson 1 Forces and Motion
Get a Move On
How is motion described?
• Position is the location of an object.
• Motion is an object’s change in position relative
to a reference point.
• Whenever your position changes, you are in
motion.
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Unit 4 Lesson 1 Forces and Motion
How is motion described?
• A reference point is a place or object to which
another object is compared.
• Whenever describing position and motion, a
reference point is used for clarity.
• Distance traveled is a way to measure the change
in position of an object.
• Displacement is the straight-line distance
between a starting point and an end point.
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Unit 4 Lesson 1 Forces and Motion
Beep Beep!
How is speed described?
• Speed is the measure of how quickly distance
changes with time.
• Meters per second (m/s) is the standard unit of
measurement for speed.
• Speed is also commonly stated in kilometers per
hour or miles per hour.
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Unit 4 Lesson 1 Forces and Motion
How is speed described?
• Instantaneous speed is the speed of an object
at a specific instant in time.
• The instantaneous speed may be very different
from the average speed.
• An object’s changing speed can be shown on a
graph with distance traveled on the y-axis and
time on the x-axis.
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Unit 4 Lesson 1 Forces and Motion
How Fast? Which Way?
How is velocity described?
• The velocity of an object is its speed combined
with the direction of motion.
• The terms speed and velocity should not be used
interchangeably.
• Why can objects moving at the same speed have
different velocities?
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Unit 4 Lesson 1 Forces and Motion
How is velocity described?
• A vector quantity is a physical quantity that has
both size and direction.
• Velocity is a vector quantity, which can be shown
on a diagram with an arrow.
• The arrow’s length represents the relative speed
of the object, while the arrow’s direction indicates
the direction of motion.
• Average velocity is calculated as the total
displacement over the total time elapsed.
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Unit 4 Lesson 1 Forces and Motion
Try to Keep Up
How is acceleration described?
• Acceleration is a measure of how quickly velocity
changes.
• Acceleration describes the change in velocity
(m/s) over time (s), so it is measured in m/s2
• You can think of acceleration as a change in
speed, direction, or both.
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Unit 4 Lesson 1 Forces and Motion
Accelerate This!
What is the relationship between
velocity and acceleration?
• Acceleration is also vector quantity and it is a
change in velocity.
• When velocity is not changing, acceleration is
zero.
• On a graph of velocity versus time, acceleration is
shown by movement up or down.
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Unit 4 Lesson 1 Forces and Motion
What is the relationship between
velocity and acceleration?
• Acceleration can be an increase or a decrease in
velocity.
• If velocity and acceleration are in the same
direction, the speed of an object is increasing.
• If velocity and acceleration are in opposite
directions, the speed of and object is decreasing.
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Unit 4 Lesson 1 Forces and Motion
What is the relationship between
velocity and acceleration?
• A change in an object’s direction is also
acceleration.
• Average acceleration is equal to the change in
velocity divided by the time over which that
change occurs.
• On a velocity-versus-time graph, a straight line
means constant acceleration, a rising line
represents positive acceleration, and a falling
represents negative acceleration.
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