Chapter 2 Section 1 Displacement and Velocity and

Chapter 2 Section 1 Displacement and Velocity and Speed • Velocity describes motion with both direction and magnitude (a numerical value). • Speed has no direction, only magnitude. • Average speed is equal to the total distance traveled divided by the time interval. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 2 Section 1 Displacement and Velocity Displacement • Displacement is a change in position. • Displacement is not always equal to the distance traveled. • The SI unit of displacement is the meter, m. Dx = xf – xi displacement = final position – initial position Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 2 Section 1 Displacement and Velocity Average Velocity • Average velocity is the total displacement divided by the time interval during which the displacement occurred. • In SI, the unit of velocity is meters per second, abbreviated as m/s. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 2 Section 1 Displacement and Velocity Conceptual Problems (from lab) • A book is moved once around the edge of a tabletop with dimensions 1. 75 m x 2. 25 m. If the book ends up at its initial position, what is its displacement? If it completes its motion in 23 s, what is its average velocity? What is its average speed? • Car A travels from New York to Miami at a speed of 25 m/s. Car B travels from New York to Chicago, also at a speed of 25 m/s. Are the velocities of the cars equal? Explain. • A bus travels 280. km south along a straight path with an average velocity of 88. km/hr to the south. The bus stops for 24. minutes. Then it travels 210. km south with an average velocity of 75. km/hr to the south. A) How long does the total trip last? B) What is the average velocity for the total trip? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 2 Section 1 Displacement and Velocity Interpreting Velocity Graphically • If the velocity is constant, the graph of x vs t is a straight line. The slope indicates the velocity. Object 1: positive velocity Object 2: zero velocity Object 3: negative velocity Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 2 Section 1 Displacement and Velocity Interpreting Velocity Graphically, continued Instantaneous velocity The instantaneous velocity at a given time can be determined by calculating the slope of the tangent line. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 2 Section 2 Acceleration Changes in Velocity • Acceleration is the rate at which velocity changes over time. • An object accelerates if its speed, direction, or both change. • The slope of the velocity-time graph is the average acceleration. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 2 Section 1 Displacement and Velocity Section Review • If a passenger train is traveling on a straight track with a negative velocity and a positive acceleration, is it speeding up or slowing down? • Sally travels by car from one city to another. She drives for 30. 0 min at 80. 0 km/hr, 12. 0 min at 105 km/hr and 45. 0 min at 40. 0 km/hr, and she spends 15. 0 min eating lunch and buying gas. – Determine the total distance traveled. – Determine the average speed for the trip. • Graph review wkst Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.