11.3 Acceleration The basketball constantly ______________ velocity as it rises and falls.

1. 11.3 Acceleration The basketball constantly ______________ velocity as it rises and falls. Describing changes in velocity, and how ___________they occur, is a part of describing motion. changes fast

2. Key Concepts • How are changes in velocity described? • How can you calculate acceleration? • How does a speed-time graph indicate acceleration? • What is instantaneous acceleration?

3. What Is Acceleration? The rate at which velocity changes is called ___________________. Recall that velocity is a combination of ______________ and ________________ So acceleration may result for changes in _____________, changes in ______________, or changes in _________ acceleration speed direction speed direction both

4. What Is Acceleration? • Since acceleration is affected by direction, it is considered a ________________. • Acceleration can be caused by _____________, (increasing) speed or by _______________ (decreasing) speed. • Negative acceleration is called ______________...it slows an object’s speed. vector positive negative deceleration

5. Acceleration Example! • When you are sitting on a bus and it starts moving, you are pushed __________ against your seat • Positive acceleration • When the bus is moving at a constant speed, the acceleration is ____________ • When the bus approaches a stop light, it begins to slow down…this time you feel pulled _____________ from your seat • Deceleration back zero away

6. What Is Acceleration? Free fall isthe movement of an object toward Earth solely because of _____________. The unit for acceleration, is meters per second squared…____________ Objects falling near Earth’s surface accelerate downward at a rate of ___________ gravity m/s2 9.8 m/s2

7. What Is Acceleration? t = 0 sv = 0 m/s At time = 0 s, what is the velocity of the rock? At time = 1 s, what is the velocity of the rock? At time = 2 s, what is the velocity of the rock? At time = 3 s, what is the velocity of the rock? t = 1 sv = 9.8 m/s 0 m/s t = 2 sv = 19.6 m/s 9.8 m/s 19.6 m/s t = 3 sv = 29.4 m/s 29.4 m/s

8. What Is Acceleration? t = 0 sv = 0 m/s What happens to the distance traveled between each second? t = 1 sv = 9.8 m/s t = 2 sv = 19.6 m/s It increases (due to faster speed) t = 3 sv = 29.4 m/s

9. What Is Acceleration? Changes in Direction Acceleration can be the result of a change in direction at constant speed, for example, riding a bicycle around a curve.

10. What Is Acceleration? constant A horse on the carousel is traveling at a _________________ speed, but it is accelerating because its _________________ is constantly changing. You feel pushed in a certain direction direction

11. What Is Acceleration? Changes in Speed and Direction Sometimes motion is characterized by changes in __________ speed and direction at the same time. both

12. What Is Acceleration? Constant Acceleration • Constant acceleration is a _______________ ______________ in velocity. steady change • An airplane’s acceleration may be constant during a portion of its takeoff.

13. Calculating Acceleration • You calculate acceleration for straight-line • motion by dividing the ____________________ • by the _____________________. • Vf = _______________ velocity • Vi = _______________ velocity change in velocity Total time final initial

14. Calculating Acceleration If the velocity increases, the acceleration is ________________. ex: coasting downhill on a bicycle If the velocity decreases, the acceleration is _________________. • Ex: coasting on level ground and slowing down positive negative

15. Calculating Acceleration A ball rolls down a ramp, starting from rest. After 2 seconds, its velocity is 6 meters per second. What is the acceleration of the ball? Vf = Vi = T = 6 m/s 6 m/s – 0 m/s 0 m/s 3 m/s2 2 s 2 s

16. A car traveling at 10 m/s starts to decelerate steadily. It comes to a complete stop in 20 seconds. What is its acceleration? Vf = Vi = T = 0 m/s 0 m/s – 10 m/s = - 0.5 m/s2 10 m/s 20 s 20 s

17. Graphs of Accelerated Motion speed-time graph The slope of a __________________ is acceleration. The acceleration of the skier is… 4 m/s = 4 m/s2 1 s

18. Graphs of Accelerated Motion constant rolls This graph shows bikers moving at a ______________ speed and then _________________to a stop. Is this change in speed positive or negative? negative

19. Graphs of Accelerated Motion distance - time curve A _________________________ graph of accelerated motion is a ________________. This is an example of a _____________ graph At which second is speed the highest? nonlinear 5 s

20. Instantaneous Acceleration Instantaneous acceleration is how fast a velocity is changing at a specific ________________. Acceleration is _______________ constant, and motion is rarely in a straight line. instant rarely

21. Assessment Questions • What is acceleration? • the rate at which speed increases • the time an object’s velocity increases • the rate at which displacement changes • the rate at which velocity changes

22. Assessment Questions • A sports car can accelerate from 0 m/s to 28 m/s in four seconds. What is the acceleration of the car? • 24 s • 7 m/s2 • 27 m/s • 27 m/s2

23. Assessment Questions 3. Which of the following is an example of negative acceleration? • Mike starts riding his bike and uses the pedals to go from 0 km/h to 20 km/h. • Mike pedals up a hill and gradually slows from 20 km/h to 5 km/h. • Mike sits on his bike at the top of the hill and rests. • Mike coasts downhill without pedalling, going from 0 km/h to 15 km/h.

24. Assessment Questions 4. The acceleration at a specific point on a distance-time graph is the • instantaneous acceleration. • momentary acceleration. • positive acceleration. • numerical acceleration.