Welcome back to Physics 211

1. Welcome back to Physics 211 Today’s agenda: Midterm #1 Thursday 9/29 Review session ? Stolkin Auditorium – 6:00 pm - SPS Vector components Motion in 2-D Read ch.3, ch. 4 through p. 102. Read ch. 4 complete! PHY211 Fall 2010 Lecture 4-1

2. Homework (WHW IV) • Due Wednesday 9/21/11 • Chapter 3 text • E&P – 3, 10, 23, 37 • Chapter 4 text • E&P – 5, 6, 11, 12, 45, 46, 50 PHY211 Fall 2010 Lecture 4-1

3. Homework (FHW IV) • Chapter 4 text • E&P – 21, 22, 27, 36, 62, 63, 67, 71 PHY211 Fall 2010 Lecture 4-1

4. Exam 1: Thursday (9/29/11) • During normal lecture period, 11:00AM - 12:20 pm in Stolkin Auditorium. • Seating arrangement by last name will be posted outside Stolkin. • Exam is closed book, but you may bring calculator and one handwritten 8.5” x 11” sheet of notes. • Practice exam problems posted on website and Wednesday in recitation workshop. • Review session (SPS) -- Wednesday, 6 - ? pm, Stolkin Auditorium PHY211 Fall 2010 Lecture 4-1

5. Exam 1: Thursday (9/29/2011) • Seating arrangement will be posted outside Stolkin • Material covered: • Textbook chapters 1, 2, 3, and 4 • Lectures up to 9/26 (slides online) • Workshops on Velocity, Acceleration in one dimension, and Motion in two dimensions • Homework assignments PHY211 Fall 2010 Lecture 4-1

6. Skill Set Mastery • Draw a Motion Diagram • Construct a s-t graph • Construct a v-t graph • Describe the motions PHY211 Fall 2010 Lecture 4-1

7. Kinematics in 2-D Topics: Acceleration Kinematics in Two Dimensions Projectile Motion Relative Motion Uniform Circular Motion Velocity and Acceleration in Uniform Circular Motion Nonuniform Circular Motion and Angular Acceleration PHY211 Fall 2010 Lecture 4-1

8. Projectile Motion PHY211 Fall 2010 Lecture 4-1

9. Simultaneous Projectile • Demo • Which hits first? • 1 – Straight down • 2 – Straight out • 3 – Same time • 4 – Not enough information • 5 – Depends on vx PHY211 Fall 2010 Lecture 4-1

10. Projectile Motion Projectile motion is made up of two independent motions: uniform motion at constant velocity in the horizontal direction and free-fall motion in the vertical direction. The kinematic equations that describe these two motions are PHY211 Fall 2010 Lecture 4-1

11. Ball Launcher Cart • Demo • Ball land in car • Ball land in front of car • Ball land behind car • Depends on speed of car • Not enough information to determine PHY211 Fall 2010 Lecture 4-1

12. Car driving off cliff How far away does the car land? What is the velocity when it lands? How long is it in the air? PHY211 Fall 2010 Lecture 4-1

13. Motion Along Curved Paths Ds =sf - si sI sF O v = Ds/Dt lies along dotted line. As Dt  0 direction of v is tangent to path PHY211 Fall 2010 Lecture 4-1

14. Motion on a curved pathat constant speed PHY211 Fall 2010 Lecture 4-1

15. A child is riding a bicycle on a level street. The velocity and acceleration vectors of the child at a given time are shown. Which of the following velocity vectors may represent the velocity at a later time? a 1. 2. 3. 4. PHY211 Fall 2010 Lecture 4-1

16. A biker is riding at constant speed clockwise on the oval track shown below. Which vector correctly describes the acceleration at the point indicated? PHY211 Fall 2010 Lecture 4-1

17. Biker moving around oval at constant speed As point D is moved closer to C, angle approaches 90°. PHY211 Fall 2010 Lecture 4-1

18. Summary • For motion at constant speed, instantaneous acceleration vector is perpendicular to velocity vector • Points “inward’’ • What is the magnitude of the acceleration vector? PHY211 Fall 2010 Lecture 4-1

19. Acceleration vectors for ball swung in a horizontal circle at constant speed v v1 q v2 R v1 q v2 What is the magnitude of the acceleration?a = v2/R PHY211 Fall 2010 Lecture 4-1

20. Angular Displacement and Derivatives θ, θ/ t θ t PHY211 Fall 2010 Lecture 4-1

21. Acceleration of object moving at constant speed on a circular path: Acceleration depends on radius of circle. PHY211 Fall 2010 Lecture 4-1

22. What if the speed is changing? • Consider acceleration for object on curved path starting from rest • Initially, v2/r = 0, so no radial acceleration • But a is not zero! It must be parallel to velocity PHY211 Fall 2010 Lecture 4-1

23. Acceleration vectors for object speeding up:Tangential and radial components(or parallel and perpendicular) PHY211 Fall 2010 Lecture 4-1

24. Sample problem • A Ferris wheel with diameter 14.0 m, which rotates counter-clockwise, is just starting up. At a given instant, a passenger on the rim of the wheel and passing through the lowest point of his circular motion is moving at 3.00 m/s and is gaining speed at a rate of 0.500 m/s2. (a) Find the magnitude and the direction of the passenger’s acceleration at this instant. (b) Sketch the Ferris wheel and passenger showing his velocity and acceleration vectors. PHY211 Fall 2010 Lecture 4-1

25. Angular Acceleration  t PHY211 Fall 2010 Lecture 4-1

26. Table 4.1 p. 116 PHY211 Fall 2010 Lecture 4-1

27. Homework (WHW IV) • Due Wednesday 9/21/10 • Chapter 3 text • E&P – 3, 10, 23, 37 • Chapter 4 text • E&P – 5, 6, 11, 12, 45, 46, 50 PHY211 Fall 2010 Lecture 4-1

28. Homework (FHW IV) • Chapter 4 text • E&P – 21, 22, 27, 36, 62, 63, 67, 71 PHY211 Fall 2010 Lecture 4-1