Before Warm up Problem

1. Before Warm up Problem Go onto Turnitin.com and make sure you can log into the correct period Code/Password • Period1 – 8549371 / JecaPhys1 • Period 3 – 8549395 / JecaPhys3 • Period 4 – 8549411 / JecaPhys4 • Period 6 – 8549441 / JecaPhys6 • Period 7 – 8554589 / JecaPhys7 • Period 8 – 8554628 / JecaPhys8

2. Warm up Problem A bus travels 280 km south along a straight path with an average velocity of 24.4 m/s to the south. The bus stops for 24 min, then it travels 210 km south with an average velocity of 20.8 m/s to the south. a. How long does the total trip last? b. What is the average velocity for the total trip?

3. Physics Honors A & B – Day 9/10/13 & 9/11/13 Motion in 1D cont.

4. Agenda • Acceleration? • velocity v. time plots • Kinematic equations • examples

5. What is acceleration?

6. Acceleration • Acceleration measures the rate of change in velocity per time • Units • Acceleration is a vector • Positive or negative means left or right direction

7. Acceleration • Direction of acceleration will affect the magnitude and direction of velocity. • Depending on Velocity vector, it could cause speeding up or slowing down.

8. Acceleration • Direction of acceleration will affect the magnitude and direction of velocity. • Depending on Velocity vector, it could cause speeding up or slowing down.

9. Acceleration • Direction of acceleration will affect the magnitude and direction of velocity. • Depending on Velocity vector, it could cause speeding up or slowing down.

10. Acceleration • Direction of acceleration will affect the magnitude and direction of velocity. • Depending on Velocity vector, it could cause speeding up or slowing down.

11. Acceleration +v and +a speed up +v and –a slow down -v and –a speed up -v and +a slow down v = 0 and + a speed up in direction of a v = 0 and –a speed up in direction of a + v and a = 0 constant velocity (No change) -v and a = 0 constant velocity (No change)

12. Acceleration • Recall rate of change in velocity • Slope If velocity went on the y-axis And t went on the x-axis

13. Velocity v. time plot

14. Velocity v. time plot Use

15. Velocity v. time plot

16. So let’s look back • How would you get from a Position v. time plot to acceleration v. time

17. Calculate acceleration from Position v. time plot What would be ?

18. Calculate acceleration from Position v. time plot What would be ?

19. Calculate acceleration from Position v. time plot What would be ?

20. But we have word problems • How are we going to solve the word problems we normally get?

21. Kinematic Equations for constant acceleration • All equations valid for constant acceleration

22. Example • A car accelerates uniformly from rest to a velocity of +23.7 m/s in 6.5 s. a) What was it’s acceleration? b) What was the car’s displacement? • Draw a picture. • Write down the given values. • Write down what we are looking for. • Write down the equation we need to use. • Convert units. • Manipulate equation. • Input number with units. • Calculate answer with correct units. • Clearly mark answer.

23. Example • A car with an initial speed of +4.0 accelerates uniformly at a rate of +3.0 . Find the final velocity and the displacement after 5.0 s. • Draw a picture. • Write down the given values. • Write down what we are looking for. • Write down the equation we need to use. • Convert units. • Manipulate equation. • Input number with units. • Calculate answer with correct units. • Clearly mark answer.