Unit 4 Lesson 1 Matter in Motion Copyright © Houghton Mifflin Harcourt Publishing Company

Get a Move On How is motion described? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

How is motion described? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

Beep Beep! How is speed described? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

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. Copyright © Houghton Mifflin Harcourt Publishing Company

How Fast? Which Way? How is velocity described? 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? Copyright © Houghton Mifflin Harcourt Publishing Company

How is velocity described? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

Try to Keep Up How is acceleration described? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

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. Copyright © Houghton Mifflin Harcourt Publishing Company

What is the relationship between velocity and acceleration? 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. Copyright © Houghton Mifflin Harcourt Publishing Company

What is the relationship between velocity and acceleration? 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. Copyright © Houghton Mifflin Harcourt Publishing Company