1. Uniform Acceleration Section 2.3 & 2.4 in Textbook. Pages 32 - 38

2. Uniform Acceleration Acceleration that does not change with time is called uniform acceleration. In this case, what will a velocity time graph of the object look like?

3. Finding the velocity equation So, when time is zero, the velocity is called the “initial velocity” or v i. The slope of a velocity-time graph is the acceleration or a. So, the equation for the velocity time graph is : v f = v i + at

4. Using the equation So, if we are given any three of the variables in this equation, we can solve for the fourth! Example 1: If a car with a velocity of 2.0 m/s accelerates at a rate of 4.0 m/s 2, what is its velocity after 2.5 s?

5. How to solve 1. If possible, draw a picture. 2. On your picture, identify which direction is positive. 3. Write down what you know. 4. Put the numbers into the equation and solve.

6. Other equations There are several other equations that will be useful to us: 1. v f = v i + at 2. v ave = ½(v f – v i ) 3. d = v i t + ½at 2 4. v f 2 = v i 2 + 2ad

7. Solving Problems using all equations We follow the same steps as earlier to solve problems using these equations. 1. If possible, draw a picture. 2. On your picture, identify which direction is positive. 3. Write down what you know and what you are looking for. 4. Write down the equation that best suits the problem. 5. Put the numbers into the equation and solve.

8. Examples 2.A policeman traveling 16.7 m/s spots a speeder ahead so he accelerates at 2.22 m/s 2 for 4.00 s. How far does he go in this time?

9. Examples 3.A motorcross rider is traveling at 18.0 m/s when he collides with a haystack and is brought to rest in a distance of 4.5 m. What is the average acceleration?

10. Example 4.On a certain planet, a ball drops 0.80 m in 2.00 s when released from rest. How fast does it accelerate?

11. Special case: Falling objects Sometimes, we discuss objects that are travelling straight up or straight down. Such objects are affected by gravity. Falling objects on earth have an acceleration of approximately 9.8 m/s 2 downward. Therefore, when we get a problem with a falling object, we say that a = -9.8m/s 2 if up is our positive direction.

12. Example 5. A golf ball is dropped from the top of the CN tower. Assuming that the ball is in true free fall (negligible air resistance) answer these questions: a) How fast will the ball be falling after 1.0 s? b) How far down will the ball have travelled after 1.0 s?

13. Your Assignment Complete the following questions from the text book: pg 38 – 39 # 1 - 9 pg 40 # 8 - 16 These questions are due on Thursday. Try them over the weekend so you can come in for help on Wednesday if necessary.