1. Motion Graph (time and distance)  You are to mark a starting line.  You are going to walk at a normal pace.  Your partner will mark with tape the distance traveled in 10 second intervals for a total of one min.  Have students measure the distance traveled during each time period, and use their data to make a motion graph.

2. Acceleration  Acceleration is the rate at which velocity changes.  Acceleration involves a change in either of these components.  In science, acceleration refers to increasing speed, decreasing speed, or changing direction.

3. Decrease in Speed  Any time the speed of an object changes, the object experiences acceleration.  That change can be an increase of decrease.  A decrease in speed is sometimes called deceleration or negative acceleration.

4. Change of Direction  An object that is changing direction is also acceleration, even if its moving at a constant speed,  A car moving around a curve or changing lanes at a constant speed is accelerating because it is changing direction.

5. Changing Direction  Many objects continuously change direction without changing speed.  An example of motion is circular motion.  The moon accelerates because it is continuously changing direction as it revolves around Earth.

6. Acceleration  Acceleration describes the rate at which velocity changes.  To determine the acceleration of an object moving in a straight line, you must calculate the change in speed per unit of time

7. Acceleration Formula  Acceleration = Final Velocity - Initial Velocity Time

8. Calculation Acceleration  As a roller coaster car starts down a slope, its speed is 4m/s.  But 3 seconds later at the bottom, its speed is 22m/s.  What is its average acceleration?

9. Information Given  Initial speed is 4m/s  Final speed is 22m/s  Time is 3s

10. Acceleration = final speed – initial speed Time  Acceleration = 22m/s – 4m/s 3s  Acceleration = 18m/s 3s  Acceleration = 6m/s 2

11. Practice Problems Calculation Acceleration 1. A falling raindrop accelerates from 10m/s to 30m/s in 2 seconds. What is the raindrop’s average acceleration? 2. A certain car can accelerate from rest to 27m/s in 9 seconds. Find the cars average acceleration

12. Answers 1. (30m/s – 10 m/s) = 10m/s 2 2s 2. (27m/s – 0m/s) = 3m/s 2 9s

13. How Velocity is Measured  If velocity is measured in meters/second and time is measured in seconds, the unit of acceleration is meters per second, which is written at m/s2

14. Graphs  You can use both a speed- verse time graph and a distance versus time graph to analyze the motion of an acceleration object.  When a graph shows speed versus time as a slanted straight line the acceleration is constant.

15. Finding Acceleration  You can find acceleration by calculation the slope of the line.  If an object accelerates by a different amount each time period, a graph of its acceleration will not be a straight line.  A graph of distance versus time for an acceleration objects is curved.