1. 10.2 Acceleration I CAN: -IDENTIFY THAT ACCELERATION IS A VECTOR PROPERTY. -CALCULATE AVERAGE ACCELERATION OF AN OBJECT. -DETERMINE IF ACCELERATION IS POSITIVE OR NEGATIVE. -DISTINGUISH BETWEEN CONSTANT AND ZERO ACCELERATION. -RECOGNIZE CONSTANT ACCELERATION.

2. Acceleration  Acceleration: the rate at which velocity changes over time.  An object accelerates if its SPEED, DIRECTION, OR BOTH change.  What about slowing down?  Typically what you think of as acceleration also increases velocity.

3. Example of changing speed  You are facing south on your bike and start moving. You speed up as you go. Every second, your southward velocity increases. After 1s, your velocity is 1m/s south. After 2s, your velocity is 2m/s south and so on… Your acceleration can be expressed as an increase of one meter per second per second (1m/s/s or 1m/s 2 )

4. Example of changing direction  Skaters on the ice, each lap in Nascar, the moon around Earth, riding a Ferris wheel!  Acceleration is defined as the rate in which velocity changes.  Velocity includes both speed AND direction.  You can actually accelerate without ever speeding up or slowing down.  What about standing still on Earth?

5. Circular Motion  An object traveling in a circular motion is always changing direction.  Acceleration that occurs in uniform circular motion is known as Centripetal Acceleration.

6. Calculating Acceleration  Acceleration= final velocity-initial velocity/change in time  Can be positive or negative  Ex: You are rollerblading and see a large rock in your path, so you slow down and swerve. Friend says, “Wow that was great acceleration.”  Is he correct?

7.  I am accelerating to a stop. I was originally going at 20m/s and stopped in 0.50 s.  Solve…  Answer: -40 m/s/s or -40 m/s 2 Practice acceleration

8.  Previously learned that an objects speed can be determine from a distance/time graph.  Acceleration can be determined from a velocity/time graph.  What does the straight line represent?  Which would be positive acceleration?  Which would be negative acceleration? Velocity-time graph

9. Homework Practice Problems (pg.328)  Natalie accelerates her skateboard along a straight path from 0 m/s to 4.0 m/s in 2.5 s. Find her average acceleration.  A turtle swimming in a straight line toward the shore has a speed of 0.50 m/s. After 4.0 s, its speed is 0.80 m/s. What is the turtles average acceleration?  Find the average acceleration of a northbound subway train that slows down from 12 m/s to 9.6 m/s in 0.8 s.  Marisa’s car accelerates at an average rate of 2.6 m/s 2. Calculate how long it takes her car to speed up from 24.6 m/s to 26.8 m/s.  A cyclist travels at a constant velocity of 4.5 m/s westward, and then speeds up with a steady acceleration of 2.3 m/s 2. Calculate the cyclist’s speed after accelerating for 5.0 s.