1. What is Velocity? What is Acceleration?

2.  Mrs. Wilk drove to school this morning. Her average speed was 27 mph. What was Mrs. Wilk’s average speed this morning? What was Mrs. Wilk’s average speed this morning? 27mph27mph  What was Mrs. Wilk’s velocity? 27mph to school 27mph to school  Velocity is defined as: A vector quantity that tells how fast an object is moving and in what direction it is moving A vector quantity that tells how fast an object is moving and in what direction it is moving Speed with direction Speed with direction

3.  What is a vector quantity? A quantity that includes direction. A quantity that includes direction.  How does one know that something is a vector quantity? Boldface type or ½ arrow Boldface type or ½ arrow or v or v

4.  Example: The speedometer of a car moving northward reads 60 mph. It passes another car traveling southward at 60 mph.  Do the cars have the same speed? Yes---60mph Yes---60mph  Do the cars have the same velocity? No because they are moving different directions No because they are moving different directions  Why is a car’s gauge called a speedometer and not a velociometer? Because it does not show direction Because it does not show direction

5.  The velocity equation:  In words: Velocity = distance / time * with direction Velocity = distance / time * with direction  In symbols: V = d/t V = d/t The wheel The wheel d vt

6.  What is constant speed? Equal distances covered in equal amounts of time Equal distances covered in equal amounts of time  What is constant velocity? Constant speed with constant direction Constant speed with constant direction  Watch the battery operated car: Constant speed and constant velocity

7.  What is changing velocity?  Watch the battery operated car: Is the speed constant? Is the speed constant? Yes– the car is moving = distances in = time periodsYes– the car is moving = distances in = time periods Is the velocity constant? Is the velocity constant? No– because the direction is constantly changing.No– because the direction is constantly changing.

8.  There are 4 controls on a car that can change the velocity. Do you know what they are?  1. gas pedal  2. brake pedal  3. steering wheel  4. transmission

9.  We can change the state of motion of an object by changing: 1. its speed 1. its speed 2. its direction of motion 2. its direction of motion 3. both its speed and direction 3. both its speed and direction  Any of these changes is considered a change in an object’s velocity.

10.  Sometimes we are interested in how fast the velocity is changing. This is called an object’s acceleration.  What is acceleration? A rate measuring how fast an object’s velocity is changing per unit of time. A rate measuring how fast an object’s velocity is changing per unit of time.

11.  The acceleration equation:  In words: Acceleration = change in velocity / time Acceleration = change in velocity / time  In symbols: a = v / t a = v / t The wheel: The wheel: at v

12. OR V f = Final Velocity V i = Initial