copyright © houghton mifflin harcourt publishing company unit 1 lesson 1
TRANSCRIPT
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 1 Lesson 1
Location, location, location
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How can you describe the location of an object?• Position describes the location of an object.
• Comparisons using known objects or locations often are used to describe position.
• A reference point is a location to which you compare other locations.
Unit 1 Lesson 1 Motion and Speed
MOVE It!
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What is motion?
• Motion is a change in position over time.
• Even when motion is not observed directly, starting points and end points can indicate motion has occurred.
Unit 1 Lesson 1 Motion and Speed
How is distance measured?
• Distance can be measured as a straight line between two positions.
• Distance can also be measured as the total length of a certain path between two positions.
• The standard unit of length for distance is the meter (m).
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Unit 1 Lesson 1 Motion and Speed
What is speed?
• Speed is a measure of how far something moves in a given amount of time.
• Speed measures how quickly or slowly an object changes its position.
• Fast objects move farther than slower objects in the same amount of time.
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Unit 1 Lesson 1 Motion and Speed
What is average speed?
• Average speed is a way to calculate the speed of an object that may not always be moving at a constant speed.
• Average speed describes the speed over a stretch of time rather than at any exact moment in time.
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Unit 1 Lesson 1 Motion and Speed
Speed It Up!
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How is average speed calculated?
• Speed can be calculated by dividing the distance an object travels by the time it takes to cover that distance.
• speed = distance/time
• s = d/t
Unit 1 Lesson 1 Motion and Speed
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How is average speed calculated?
• If two objects travel the same distance, the object that takes less time has the greater speed.
• An object with a greater speed travels farther in the same time than an object with a lower speed travels.
• The standard unit for speed is meters per second (m/s).
Unit 1 Lesson 1 Motion and Speed
Fast Graphs
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How is constant speed graphed?
• Distance-time graphs are used to plot the distance an object travels over time.
• The distance of an object away from a reference point is plotted on the y-axis. Time is plotted on the x-axis.
• Objects moving at a constant speed make a straight line on the graph.
Unit 1 Lesson 1 Motion and Speed
How is constant speed graphed?
• The slope, or steepness, of the line is equal to the average speed of the object.
• Average speed can be calculated by dividing the change in distance by the change in time for that time interval.
• slope = change in y/change in x
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Unit 1 Lesson 1 Motion and Speed
How are changing speeds graphed?
• On a distance-line graph, a change in the slope of a line indicates a change in speed.
• If the line gets steeper, the object’s speed has increased.
• If the line gets less steep, the object has slowed down.
• A flat line indicates zero speed.
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Unit 1 Lesson 1 Motion and Speed
Follow Directions
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What is velocity?
• A vector is a quantity that has both size and direction.
• Velocity is speed in a specific direction.
• Objects can have the same speed but different velocities because of their direction of travel.
Unit 1 Lesson 1 Motion and Speed
What is velocity?
• Average velocity depends on the distance from the starting point to the final point.
• Average velocity can be 0 km/h if you travel at a certain speed to one point and then travel back to the starting point.
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Unit 1 Lesson 1 Motion and Speed
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Unit 1 Lesson 2
Acceleration
Getting up to Speed
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How do we measure changing velocity?
• Acceleration is the rate at which velocity changes.
• An object accelerates if its speed, direction, or both change.
• Acceleration depends on how much velocity changes and how much time that change takes.
Unit 1 Lesson 2 Acceleration
How do we measure changing velocity?
• What is the change in velocity for each second of time that passes?
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Unit 1 Lesson 2 Acceleration
How is average acceleration calculated?• Average acceleration = (final velocity – starting velocity)/time
• a = (v2 – v1)/t
• Acceleration is measured in meters per second squared (m/s2).
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Unit 1 Lesson 2 Acceleration
What a Drag!
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How can accelerating objects change velocity?• Acceleration refers to both increases and decreases in speed. A change in direction is also acceleration.
• An increase in velocity is called positive acceleration.
• A decrease in velocity is called negative acceleration.
Unit 1 Lesson 2 Acceleration
How can accelerating objects change velocity?• Is the horse showing negative acceleration or positive acceleration? Explain.
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Unit 1 Lesson 2 Acceleration
How can accelerating objects change velocity?• An object traveling in a circular motion is always changing its direction, and so it always experiences acceleration.
• Centripetal acceleration is acceleration in a circular motion.
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Unit 1 Lesson 2 Acceleration