Chapter 3 - Motion

Unit Objectives Distinguish between distance and displacement. Calculate the average speed of an object. Explain the difference between speed and velocity. Write equations for the displacement and velocity of an object over time. Recognize and draw graphs of an objects displacement and velocity verses time. Describe how acceleration, time and velocity are related. Explain how positive and negative acceleration affect motion. Interpret motion diagrams Explain how forces and motion are related. Compare and contrast static friction and sliding friction. Describe the effects of air resistance on falling objects.

3.1 Notes - Motion With Lecture Tutorial

Today’s Objectives Distinguish between distance and displacement.

Physics of Motion Mechanics = the study of the motion of objects (physics of motion) Kinematics = using words to describe the motion of objects Used to develop models that describe the motion of real-world objects

New Vocabulary Scalar quantity = fully described by a magnitude (or numerical value) alone. Vector quantity = fully described by both a magnitude and a direction. Khan Academy Video

Examples Quantity Category a. 5 m b. 30 m/sec, East c. 5 mi., North d. 20 degrees Celsius e. 256 bytes f. 4000 Calories Scalar Vector Vector Scalar Scalar Scalar

Motion Occurs when an object changes position Position depends on a reference frame

Distance The length of the path the object travels Scalar quantity Physical quality Does not have direction Not a vector refers to "how much ground an object has covered" during its motion.

Displacement Distance & direction of an object’s final position from its original Size & Direction A Vector refers to "how far out of place an object is" it is the object's overall change in position.

Distance vs. Displacement

Example Total Distance = _____ Total Displacement = _____ A physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North. 12 m Total Distance = _____ Total Displacement = _____ 0 m

Example 2 Total Distance = _____ Total Displacement = _____ 420 m The position of a cross-country skier at various times. At each of the indicated times, the skier turns around and reverses the direction of travel. In other words, the skier moves from A to B to C to D. 420 m Total Distance = _____ Total Displacement = _____ 140 m, right

Example 3 Total Distance = _____ Total Displacement = _____ 95 yds As a final example, consider a football coach pacing back and forth along the sidelines. The diagram below shows several of coach's positions at various times. At each marked position, the coach makes a "U-turn" and moves in the opposite direction. In other words, the coach moves from position A to B to C to D. 95 yds Total Distance = _____ Total Displacement = _____ 55 yds, left

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