2.  Define velocity  Give an example  ( If you have not done so – hand in your lab)

3.  Motion can be in: ◦ A straight line ◦ Circle/curved path ◦ Back and forth motion  Uniform motion ◦ The simplest kind of motion ◦ Along a straight line ◦ Feels smooth ◦ No change in velocity

4.  Un-uniform motion ◦ Along a curved or up and down path ◦ Feels bumpy  Ex: roller coasters, stop and go traffic, walk/jog/walk ◦ Change in velocity This is acceleration!!  The rate* at which an object’s velocity changes *rate = a change over time

5.  Positive acceleration ◦ Increase in velocity ◦ Speeding up  Negative acceleration ◦ Decrease in velocity ◦ Slowing down  Change in direction ◦ with or without velocity change

6. If a dog chases its tail in a circle at the same speed the whole time, is it accelerating? Yes! Even though its speed is staying constant, it is changing direction, and therefore changing its velocity. If the velocity changes, it is accelerating.

7. You are riding your bike at 9 km/hr. Ten minutes later, your speed is 6 km/hr You ride your bike around the block at a constant speed of 11 km/hr You ride your bike in a straight line at a constant speed of 10 km/hr You are stopped at a red light and then it turns green

8.  To find acceleration: A = ∆V (also written as (V f – V i ) ∆ t ∆ is the greek letter delta and means “the change in” ◦ To find the change in velocity:  final velocity of the object (V f ) minus initial velocity of the object (V i ) ◦ To find the change in time:  final time of the object’s motion (t f ) minus initial time of the object (t i )

9.  Acceleration is a unit of speed divided by a unit of time ◦ Ex: m/s/s  Can also be written as m/s 2 ◦ Ex: km/hr/s ◦ Ex: km/hr/hr  Can also be written as km/hr 2  What does this unit mean? ◦ It tells you how much velocity is changing per unit of time  Ex: 5 m/s 2  Means that velocity is increasing (because it’s a positive #) by 5 m/s every second that the object travels

10. What does it mean? – Ex 2: if a car is accelerating at a rate of 10 m/s/s then its velocity is increasing by 10 m/s every second it is traveling 1s = 10 m/s 2s = 20 m/s 3s = 30 m/s4s = 40 m/s

11.  Zero words ◦ Words that either mean the objects starts at rest (not in motion) or stops its motion ◦ Stop ◦ At rest ◦ At a standstill

12.  A jet starts at rest at the end of a runway and reaches a speed of 80 m/s in 20s. What is its acceleration? 1. Write what is given: ◦ V i = 0 m/s (it started at rest) ◦ V f = 80 m/s ◦ ∆t = 20 s 2. Solve for acceleration:

13.  A skateboarder is moving in a straight line at a speed of 3 m/s and comes to a stop in 2 seconds. What is his acceleration? 1. Write what is given: ◦ V i = 3 m/s ◦ V f = 0 m/s (came to a stop) ◦ ∆t = 2 s 2. Solve for acceleration: