1. Speed, Velocity, and Acceleration Review

2. Frame of Reference When we describe something that is moving, we are comparing it to something that is assumed to be stationary (not moving) When we describe something that is moving, we are comparing it to something that is assumed to be stationary (not moving) Usually Earth – moves very slowly Usually Earth – moves very slowly The background or object used for comparison is called a frame of reference The background or object used for comparison is called a frame of reference For example: http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_ pg7_relmotion/mfm05_pg7_relmotion.html For example: http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_ pg7_relmotion/mfm05_pg7_relmotion.html http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_ pg7_relmotion/mfm05_pg7_relmotion.html http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_ pg7_relmotion/mfm05_pg7_relmotion.html

3. Speed Three types of speed Three types of speed Constant speed – does not vary Constant speed – does not vary Average speed – distance divided by time Average speed – distance divided by time Instantaneous speed – the speed at a given moment Instantaneous speed – the speed at a given moment What type of speed does your car speedometer read? What type of speed does your car speedometer read?

4. Velocity A tornado has just been sighted in Greensboro. Does the school need to go into the tornado emergency plan? A tornado has just been sighted in Greensboro. Does the school need to go into the tornado emergency plan? What piece of information does Mr. Telford need to make a decision? What piece of information does Mr. Telford need to make a decision? Direction Direction Velocity includes both speed and direction Velocity includes both speed and direction

5. Speed and Velocity Think about driving a car. Which two controls cause a change in speed? Think about driving a car. Which two controls cause a change in speed? Accelerator Accelerator Brake Brake Which additional control causes a change in velocity? Which additional control causes a change in velocity? Steering wheel Steering wheel

6. Speed and Velocity Practice An airplane flew 1000 km in 4 hr. What is the airplane’s speed? An airplane flew 1000 km in 4 hr. What is the airplane’s speed? A car travels 50 km west in 30 minutes. What is its velocity in km/hr? A car travels 50 km west in 30 minutes. What is its velocity in km/hr? How long will it take a ball to roll 26m if its velocity is 2.0m/s to the right? How long will it take a ball to roll 26m if its velocity is 2.0m/s to the right? If a runner moves with a speed of 1.5m/s and changes her speed to 2.1m/s over 3s, what is her average speed over that 3s? If a runner moves with a speed of 1.5m/s and changes her speed to 2.1m/s over 3s, what is her average speed over that 3s?

7. Acceleration Acceleration tells you how fast velocity is changing Acceleration tells you how fast velocity is changing Formula: Formula: A=V-V A=V f -V it What are the units for acceleration? What are the units for acceleration?m s2s2s2s2 Can be positive or negative (deceleration) Can be positive or negative (deceleration)

8. Acceleration A car is stopped at a stoplight. When the light turns green, the car speeds up to 75 km/hr is 0.05 hr. What is the car’s acceleration rate? A car is stopped at a stoplight. When the light turns green, the car speeds up to 75 km/hr is 0.05 hr. What is the car’s acceleration rate? Formula: Formula: A=V-V A=V f -V it

9. Acceleration A car is traveling at 60 km/hr in a straight line. What is the car’s acceleration rate? A car is traveling at 60 km/hr in a straight line. What is the car’s acceleration rate? Formula: Formula: A=V-V A=V f -V it

10. Acceleration A car is traveling at 60 km/hr in a straight line. What is the car’s acceleration rate? A car is traveling at 60 km/hr in a straight line. What is the car’s acceleration rate? Formula: Formula: A=V-V A=V f -V it