108 Views

Download Presentation
## Review and Announcements

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -

**Review and Announcements**• Tatiana Brusentsova is the Teaching Assistant/Grader. • My office hours will take place in Room 402 of the Physics Department. • Make sure you are using WebAssign by the end of the week! Homework #1 due Monday.**Chapter 2: One-Dimensional Kinematics**• Outline • 2-1 Position, Distance, and Displacement • 2-2 Average Speed and Velocity • 2-3 Instantaneous Velocity • 2-4 Acceleration • 2-5 Motion with Constant Acceleration • 2-6 Applications of the Equations of Motion • 2-7 Freely Falling Objects**Major Concepts**• Position, distance and displacement • Speed and velocity • Average • Instantaneous • Constant • Acceleration • Average • Instantaneous • Constant • Graphs of position versus time, velocity versus time, and acceleration versus time • Equations of motion with constant acceleration • Free fall Warning Areas: Speed vs. Velocity Distance vs. Displacement Constant Velocity vs. Constant Acceleration**Distance and displacement**• Displacement is the net change in position from beginning to end of a journey • Distance is the total amount of change in position, including re-tracing your steps on the journey. Physics uses common terms in technical ways.**Figure 2-2One-Dimensional Coordinates**Try some examples…**Speed and Velocity**• Speed is the distance traveled in a period of time. It is a “scalar” (number only). • Velocity is the displacement in a period of time. It is a “vector” (number and direction).**Distance and displacement**What is the displacement at 1s, 2s, 3s, 4s? What is the distance traveled at 1, 2, 3, 4s?**What is the average speed?**• Greater than 40 mph. • Less than 40 mph. • Equal to 40 mph. Cross-Tab Label 0 / 100**What is the average speed?**• Greater than 40 mph. • Less than 40 mph. • Equal to 40 mph. Problem solving: -draw a picture -label all quantities -identify “unknown” -write down relationships (formulas), working backwards from unkown to known -find a formula for the unknown -plug in the numbers Etc. Cross-Tab Label 0 / 100**Example 2-2Sprint Training**Compare the average speed, and average velocity.**Figure 2-4Motion Along the X Axis Represented with an**x-Versus-tGraph**Figure 2-8Graphical Interpretation of Average and**Instantaneous Velocity**Our first formula!**If the velocity is constant, then the average velocity is the same as the instantaneous velocity. Rearranging:**Acceleration**• Acceleration is the change in velocity per unit time • The average acceleration is the change in velocity per change in time. It is a vector quantity.**Figure 2-9v-Versus-t Plots for Motion with Constant**Acceleration**Our second formula!**For constant acceleration… Velocity versus time produces a straight line graph, if acceleration is constant.**Figure 2-10Graphical Interpretation of Average and**Instantaneous Acceleration**Cars Accelerating or Deceleratingwhich picture matches which**graph? 1 2 3 4**Figure 2-13aThe Average Velocity**Special case: Constant acceleration Definition: change in velocity divided by time.**Figure 2-16Velocity as a Function of Position for the Ranger**in Example 2-8 Notice that ½ the speed is lost in last ¼ of stopping distance. CONSTANT DECELERATION**Example 2-9aCatching a Speeder**Q: How many mph?**Figure 2-26Problem 2-21**Find the average velocity for each segment of the “walk”, and for the total “walk”. Now, compare DISPLACEMENT and DISTANCE. Compare, average VELOCITY and SPEED.**Figure 2-28Problem 2-32**What is the average acceleration for each segment, what is the average acceleration for the whole motorcycle ride?**Figure 2-29Problem 2-33**CAREFUL! What is the displacement for each segment of the graph shown? • Problem solving: • Draw a picture (given) • What are they asking for? • What is given? • What are the mathematical relationships?