#### Transcript Mechanics - the Study of the Motion of Objects

Mechanics - the Study of the Motion of Objects Kinematics is the science of describing the motion of objects 0011 0010 1010 1101 0001 0100 1011 using words, diagrams, numbers, graphs, and equations. 1 2 4 Warm-Up Quiz 08/11/09 • Two chains of length 1.0 m are used to lamp, 0011 0010support 1010 1101a0001 0100 as 1011shown in Fig. 1.21. The distance between the two chains is 1.0 m along the ceiling. What is the vertical distance from the lamp to the ceiling? 1 2 4 Describing Motion • Scalars are quantities which are fully described by a magnitude (or numerical value) alone. 0011 0010 1010 1101 0001 0100 1011 • Vectors are quantities which are fully described by both a magnitude and a direction. • Categorize each quantity as being either a vector or a scalar a) 5 m b) 30 m/sec, East c) 5 mi., North d) 20 degrees Celsius e) 256 bytes f) 4000 Calories 1 2 4 Distance and Displacement Distance and displacement are two quantities which may seem to mean the same thing yet have 0011 0010 1010 1101 0001 0100 1011 distinctly different definitions and meanings. • Distance is a scalar quantity which refers to "how much ground an object has covered" during its motion. • Displacement is a vector quantity which refers to "how far out of place an object is"; it is the object's overall change in position. 1 2 4 Consider the motion depicted in the diagram below. A physics teacher walks 4 meters East, 2 meters South, 4 meters West, and 0011 0010 1010 1101 0001 0100 1011 finally 2 meters North. 1 2 4 The diagram below shows the position of a crosscountry skier at various times. At each of the indicated times, the skier turns around and reverses the direction of travel. In1101 other words, the skier moves from A to B to 0011 0010 1010 0001 0100 1011 C to D. Use the diagram to determine the resulting displacement and the distance traveled by the skier during these three minutes. 1 2 4 To summarize… 0011 0010 1010 1101 0001 0100 1011 • a vector quantity such as displacement is direction-aware • a scalar quantity such as distance is ignorant of direction • What is the displacement of the crosscountry team if they begin at the school, run 10 miles and finish back at the school? • What is the distance and the displacement of the race car drivers in the Indy 500 1 2 4 Speed and Velocity 0011 0010 1010 1101 0001 0100 1011 • Speed is a scalar quantity which refers to "how fast an object is moving." It is the rate at which an object covers distance. • Velocity is a vector quantity which refers to "the rate at which an object changes its position." When evaluating the velocity of an object, one must keep track of direction. • Describe your trip to school today in terms of velocity! 1 2 4 Warm-Up 08/13/10 0011 0010 1010 1101 0001 0100 1011 Please sketch a graph of your distance (y-axis) vs time (x-axis) on your trip to school Include a title, labels, units, and a dot-to-dot line (NOT a best-fit line this time). 1 Thanks! 2 4 Calculating Average Speed and Average Velocity 0011 0010 1010 1101 0001 0100 1011 1 2 • While on vacation, Lisa Carr traveled a total distance of 440 miles. Her trip took 8 hours. What was her average speed? 4 Average Speed versus Instantaneous Speed • Instantaneous Speed - the speed at any given instant in time. 0011 0010 1010 1101 0001 0100 1011 • Average Speed - the average of all instantaneous speeds; found simply by a distance/time ratio • Now let's consider the motion of that physics teacher again. The physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters • North. The entire motion lasted for 24 • seconds. Determine the average speed and • the average velocity • Now do the same for the skier using the times provided in the diagram. 1 2 4 Vector Addition and PhET Simulations Lab • • • • Please log on to the following website: http://phet.colorado.edu/ Click Play with sims On the left side, scroll down to find “Math Tools” and click it. New icons appear on the right side of the screen. Scroll down on the right side until you see “Vector Addition” and click on the icon. The program may take a few minutes to load. • Answer the questions on GRAPH PAPER 0011 0010 1010 1101 0001 0100 1011 1 2 4 Tonight’s Homework 0011 0010 1010 1101 0001 0100 1011 • p. 27-30, #49, 58, 61, 63, 72, 73, 80, 95, 96, 102 • Finish Vector Lab, if necessary • Study for Ch. 1 Quiz 1 2 4