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Motion. Chapter 15 p. 442 Standard 8-5. I Describing and Measuring Motion (p. 444). A. Recognizing Motion. 1. Motion - when one object’s distance from another is changing. 2. R eference point - object used for comparison to see if something is in motion.
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Motion Chapter 15 p. 442 Standard 8-5
I Describing and Measuring Motion (p. 444) A. Recognizing Motion • 1. Motion - when one object’s distance from another is changing • 2. Reference point - object used for comparison to see if something is in motion
B. Describing Distance/Motion (p. 50) (To describe motion, use units of measurement.) • 1. International System of Units (SI) - • the metric system • 2. The meter is the basic SI unit of length.
C. Speed (p. 446) • 1. Calculating Speed -The speed of an object is the distance something travels in one unit of time. Distance Speed = Time • 2. Constant Speed - An object moving at the same speed over a long period of time.
C. Speed (p. 446) • 3. Average Speed - An object moves at varying speeds. Total Distance Average Speed = Total Time 4. Instantaneous Speed – the speed of an object at one instant of time
Practice Problems (P.446) • A runner completes a 400 m race in 43.9s. In a 100 m race, he finishes in 10.4 s. In which race was his speed faster? • 2. A passenger train travels from Boston to New York, a distance of 350 km, in 3.5 h. What is the train’s speed?
D. Velocity – speed in a given direction (When you know both the speed and the direction of an object’s motion, you know the velocity!) • E. Motion graphs (p. 448) • 1. Time on x-axis • 2. Distance on y-axis Y Distance X Time
3. Steeper slopes = faster speed 4. Horizontal line = no change in position (distance didn’t change) 5. Straight line = constant speed (speed is not changing)
Described relative to Measured by Equals With direction is called
F. Acceleration (Sec. 2 p. 450) 1. In science, acceleration refers to increasing speed, decreasing speed, or changing direction. Which car is accelerating?
2. Acceleration- the rate at which velocity changes 3. To find acceleration of an object, you must calculate the change in velocity during each time unit. Final Velocity – Initial Velocity Acceleration = Time
Example Problem: A roller coaster starts down a hill. As it starts, its speed is 4 m/s. But 3 seconds later at the bottom of the hill, its speed is 22 m/s. What is the average acceleration? Final Velocity – Initial Velocity Acceleration = Time 22 m/s – 4 m/s Acceleration = 3 s 18 m/s Acceleration = 3s Acceleration = 6 m/s2
Compare and contrast the following graphs. Acceleration Graph Speed Graph Distance (m) Speed (m/s) Time (s) Time (s)
Practice Problems (P.446) • A runner completes a 400 m race in 43.9s. In a 100 m race, he finishes in 10.4 s. In which race was his speed faster? • 2. A passenger train travels from Boston to New York, a distance of 350 km, in 3.5 h. What is the train’s speed? • Answers: • 1.The 100 m race. (400 m= 9.11 m/s ; 100 m= or 9.62 m/s) • 2. 100 km/h