Ch. 1 - Change: ­­­­motion Two questions: ● How do we...

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Unformatted text preview: Change: ­­­­motion Two questions: ● How do we describe motion? We want to analyze the motion mathematically The mathematical description of motion is called kinematics. ● How do we explain motion? The explanation of motion in terms of its causes is called dynamics. Newton’s Law Newton’s Law Concepts of Motion Concepts of Motion • • • • • • • 1.1 Motion Diagrams 1.2 The Particle Model 1.3 Position and Time 1.4 Velocity 1.5 Acceleration 1.6 Examples of Motion Diagrams 1.7 From Words to Symbols Suggest to practice: Suggest to practice: Stop to think 1.1 P5 Stop to think 1.2 P6 Stop to think 1.3 P13 Stop to think 1.4 P15 Stop to think 1.5 P28 Example 1.2 P 12 Example 1.4 P 16 Example 1.6 P 17 Example 1.8 P 22 Example 1.9 P 23 Example 1.10 P 27 1.1 Motion Diagram 1.1 Motion Diagram • Motion is defined as the change of an object’s position with time • The right picture is showing a car positions at several equally spaced instants of time. It is motion diagram I Object moving with constant speed Ball slowing down as it rises And speeding up as it falls 1.2 Particle Model 1.2 Particle Model Particle model of motions is a simplification in which we treat a motion object as if all of its mass were concentrated at a single point. 1.3 Position and Time 1.3 Position and Time Change in Position Change in Position ttt t ∆r = r 1 − r 0 ∆r is Displacement. Vector and Vector addition Vector and Vector addition Application to Motion Diagrams Application to Motion Diagrams Velocity Velocity distance average speed = time interval spent traveling ∆ r V ( avg ) = ∆ t In Physics the distinction between speed and velocity is very important. Speed is scalar (how fast); velocity Is vector (how fast and in which direction). Motion diagrams with velocity vector Motion diagrams with velocity vector Motion diagram of a ball Motion diagram of a ball The average velocity vectors are found by connecting to dots with arrows. Relating position to velocity Relating position to velocity Acceleration Acceleration • Average acceleration ∆ v a ( avg ) = ∆ t t A particle undergoes acceleration which moving A particle undergoes acceleration which moving a from 1 to point 2. Which of the choice shows the t velocity v2 Examples of Motion Diagrams Examples of Motion Diagrams • Please practice examples 1.4­­­1.8 (page 18—20). Example 1.4 Skiing through the wood Position vs time graphs Position vs time graphs From Words to Symbols From Words to Symbols • Sketch the situation • Establish a coordinate system t ttt Define symbols. ex. • Vx Vy Vo Vf • List known information Some quantities are implied by the problem, rather than explicitly given. Others are determined by your choice of coordinate system. ●Identify the desired unknowns Units and significant figures Units and significant figures • Three basics SI unit Convert the following to SI units Convert the following to SI units • 60mi/h = 60mi ×1600m / mi = 27 m / s 1h × 3600 s / h • Alcohol mass density 0.81g/cm = 3 0.81g × 10 − 3 kg / g 2 3 = 8.1kg × 10 / m 3 −6 3 3 (cm ) × 10 × (m / cm ) ...
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This note was uploaded on 01/31/2011 for the course ACCT 2102 taught by Professor Clark during the Spring '10 term at Georgia State University, Atlanta.

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