Activating Prior Knowledge:

• Have a student blow up a balloon
• "Ask if the balloon is moving or not?"
• "Ask what could you do to make the balloon move?’
• Have the student release the balloon
• "Ask students to describe the motion of the balloon?
• In this section we will be investigating changing speed and changing direction

Go over "Guide for Reading" and "Reading Strategies" p. 104K

Reading Questions: Have the class take a few minutes to quietly read by themselves.

Have them think about these 2 questions as they read.

1. What happens to an objects motion as it accelerates?
2. How is acceleration calculated?

• Describe what happens to the motion of an object as it accelerates.
• Calculate acceleration as a change in velocity per unit of time.

• Changes in motion. Describe the changes in motion of a pitched softball. Pitcher's hand it is going 0m/s then it rapidly speeds up to full speed. When it hits the bat it rapidly slows to 0m/s then speeds up again rapidly in the opposite direction.
• It rare for motion to stay the same. Few things remain at constant speed. Objects start stop speed-up and slow down. These are changes in motion and we are going to investigate these changes.
• Acceleration: is a change in velocity. Velocity is speed and direction. So if speed changes or the direction of the object changes it has accelerated. When a car goes form a dead stop to moving it has accelerated or speeded up.
• Besides speeding up acceleration also means, decreasing speed and changing direction.
• Decreasing speed is also known as negative acceleration or more often deceleration.
• Quick quiz. True or false.

1. When you step on the gas, the car accelerates.
2. When you step on the brake the car accelerates.
3. The tricky part is when a car or an object turns. "Is it changing speed?
4. "Is it changing velocity?’ What is the difference between speed and velocity?"

• Any time we have a change in velocity we have acceleration. So anytime we change direction we are also accelerating.
• As we go around a ferris wheel, or orbit the sun we are accelerating. This is called Circular Motion, or Orbital Motion.

Calculating Acceleration. P. 34 M

• Acceleration is the rate at which an object changes velocity.
• To calculate acceleration then we need to determine the amount of velocity change.
• Final Velocity = Vf minus Initial Velocity= Vi Vf-Vi = change in velocity
• To determine how quickly this change occurs we divide by time. Vf-Vi/t this tells us how or change in velocity over a change in time. Vf-Vi/Tf-Ti much change in velocity we have each second.
• The rate or speed that an object changes velocity is its acceleration

See page 37 M for directions.

Notes: convert units so that they are all the same. Don’t forget givens.

Graphing Acceleration:

• First do a graph or constant speed.
• Then do a graph of average speed.
• Then do an acceleration graph.

Discover: " Will you Hurry Up"

Items used: Stop watches and 25 meters marked every 5 meters

Volunteer to run 25 meters

Volunteers to man stop watches at every 5 meters

Procedure: At the start signal the runner starts running and all the timers start their stopwatches. As the runner passes each timer the timer stops timing.

In class calculate the speed of the runner at each point.

Ask if his speed remained the same?

Have the class calculate the average speed for the run.

Show the class a graph of the speeds.

Assignment: Have them turn in their work showing the speeds at each point and the average speed at the end etc.

Chapter Review:

1-15, 17-20, 22,23