Chapter 6: Applied Motion Pages 238-261

Chapter 6: Applied Motion When you think about velocity changes, you might think about fast- moving race cars, but velocity changes do not have to involve high speeds. The person climbing the waterfall experiences velocity changes, but those changes involve slow speeds. What are some other examples of velocity changes? Sample answer: any form of motion will involve changes in velocity, even if only when starting or stopping

Changes in Velocity When a car is moving at constant speed—uniform motion—you are almost unaware of any motion at all. When you travel in a car that has changing speed, your body feels some of the changes. What do you think the driver of this race car is feeling as the car goes faster and faster? Sample answer: The driver feels like he or she is being pushed backwards against the seat.

Acceleration Acceleration, is a change in the velocity of an object during a time interval or a rate of change of velocity per unit of time. Acceleration can be a change in speed or a change in direction of the object. Acceleration is a vector quantity. Sample answers: Situations can include going down a hill, speeding up, slowing down, and turning. Describe two situations in which you are accelerating when you are riding a bicycle.

Graphing Accelerated Motion When an object has accelerated motion, the motion is not uniform. Position-time graphs of accelerated motion are always curved. Describe the changes in speed in each graph. Sample answers: In the first graph, the sprinter starts slowly, then increases speed. In the second graph, the sprinter starts rapidly, then decreases speed.

Graphing Accelerated Motion The slope of the line in the position-time graph (A) shows that the velocity is constant. The slope of the velocity-time graph (B) indicates that the velocity is constant; therefore, acceleration is also constant. What does the zero slope of the velocity-time graph indicate about the acceleration of the object? Sample answer: The zero slope of the velocity-time graph indicates that the acceleration of the object is zero.

Graphing Accelerated Motion The curve of the position-time graph (A) indicates that the velocity is increasing. The slope of the velocity-time graph (B) indicates that velocity is increasing and is constant. What does the slope of the velocity-time graph indicate about the acceleration of the object? Sample answer: Acceleration of the object is uniform and positive.

Graphing Accelerated Motion The curve of the position-time graph (A) indicates that the velocity is decreasing. The slope of the velocity-time graph (B) indicates that velocity is decreasing and is constant. What does the slope of the velocity-time graph indicate about the acceleration of the object? Acceleration of the object is uniform and negative.

Motion in a Car When you ride in a vehicle, such as a car, train, truck, or airplane, you feel the effects of acceleration on your body. Describe the effects of acceleration on the crash dummy when the vehicle comes to a sudden stop. Sample answer: The crash dummy is restrained by a seat belt as it is propelled forward. The head and shoulders experience whiplash as the dummy is slammed backwards when the vehicle comes to a stop.

Section 6.1 Review A change in the velocity of an object during a time interval is acceleration. The change in velocity can be a change in the speed of the object, a change in the direction of the object, or both a change in speed and direction of an object. Analyzing a position-time graph gives you information about the velocity of the object. Analyzing a velocity-time graph gives you information about the acceleration of the object. During car rides, you experience zero acceleration, positive acceleration, and negative acceleration.

Calculating Speed and Velocity UNIT 3 Chapter 6: Applied Motion Calculating Speed and Velocity The speed and velocity of an object can be calculated using the formulas below. What is the key difference between these two formulas? Sample answer: Speed is a scalar, and it has only magnitude, which is represented by a number and a unit. Velocity is a vector, and it has magnitude and direction, which is represented by a number, unit, and direction.

Calculating Acceleration The acceleration of an object can be calculated using the formula below. Acceleration will be the same direction as the change in velocity. Sample answer: The direction of acceleration is the same as the direction of the change in velocity. What is the direction of acceleration of the object?

Assignment For practice using formulas, please complete the following: Questions 4-16 on page 252-253 (Speed and Velocity) Questions 17-25 on page 256-257 (Acceleration) This is what we will be doing for today and tomorrow, though tomorrow I will have worksheets for you to have more practice. Ask me any questions as you are going along! Please complete the organizer I handed out to you, so you have all the formulas and what they mean in one spot. This will also help for studying for your unit test next week.