1. Speed, Motion, velocity, acceleration Ch. 11 & 12 Notes

2. Motion Motion  A change in position with respect to a reference point. Frame of Reference = nonmoving point from which motion is measured Reference point Motion

3. Speed Distance – total length of a path between two points. Displacement – length(straight line) and direction from a starting to an ending point. Speed - distance traveled per unit time Distance units: Time units: Speed units: How to calculate speed =>

4. Speed - practice  Florence Griffith Joyner set a world record by running 200.0 m in 21.3 seconds. What was her speed?  Suppose polar bears were running on land instead of swimming. If the polar bear runs at a speed of about 8.30 m/s, how far will it travel in 36 000 s? Put your answer in scientific notation.  How much time does it take for a bird flying at at speed of 45 km/hr to travel a distance of 1800 km?

5. Speed Instantaneous Speed  speed at a given instant Constant speed – speed that stays the same over time Average Speed- total distance traveled over total time it took to travel that distance.

6. Average Speed - practice 1. You drive 200.0 miles in 3.00 hours. Then you stop at a rest stop for Wendy’s and to gas up the car. After your stop you travel 150.0 miles in 1.50 hours. What is your average speed for the entire trip?

7. Velocity Velocity  speed in a given direction  can change even when the speed is constant! Resultant velocity – when velocities are combined  EX: bus moving at a velocity of 15 mi/hr, North  You on the bus walking, your velocity is 1 mi/ hr N  Resultant velocity = 16 mi/hr  You on the bus walking again, but this time you’re walking in opposite direction the bus is going- your velocity is -1 mi/hr South  Resultant velocity = 14 mi/hr

8. Velocity- practice If Justin races his Chevy S-10 north bound on Highway 235 for 2560.0 meters in 60.0 seconds. What is Justin’s velocity? http://www.youtube.com/watch?v=reAK FlbdhGY#t=91 http://www.youtube.com/watch?v=reAK FlbdhGY#t=91

9. Graphing Motion slope = steeper slope = straight line = flat line = Distance-Time Graph A B faster speed constant speed no motion speed

10. Acceleration Acceleration  the rate of change of velocity  change in speed or direction a: acceleration v f : final velocity v i : initial velocity t: time a v f - v i t

11. Acceleration Positive acceleration  “speeding up” Negative acceleration  “slowing down”

12. D. Calculations A roller coaster starts down a hill at 10 m/s. Three seconds later, its speed is 32 m/s. What is the roller coaster’s acceleration? GIVEN: v i = 10 m/s t = 3 s v f = 32 m/s a = ? WORK : a = ( v f - v i ) ÷ t a = (32m/s - 10m/s) ÷ (3s) a = 22 m/s ÷ 3 s a = 7.3 m/s 2 a v f - v i t

13. Distance-Time Graph E. Graphing Motion Acceleration is indicated by a curve on a Distance-Time graph. Changing slope = changing velocity

14. E. Graphing Motion Distance-Time Graph A B

15. E. Graphing Motion Speed-Time Graph slope = straight line = flat line = acceleration  +ve = speeds up  -ve = slows down constant accel. no accel. (constant velocity)

16. E. Graphing Motion Speed-Time Graph Specify the time period when the object was... slowing down  5 to 10 seconds speeding up  0 to 3 seconds moving at a constant speed  3 to 5 seconds not moving  0 & 10 seconds