1. **10 POINT DIY: Arcola Elementary, has a science fair every year and is in need of some judges. Thursday, March 26. The contact at the school is Ms. Jackie Bruley. jackie.bruley@lcps.org 1.What is speed? 2.What would you need to know in order to calculate your own speed?

2. Speed: The rate at which an object moves; speed depends on the distance traveled and the time taken to travel that distance. Formula: SI Unit: Meters / second

3. Other units commonly used to express speed… Kilometers per hour, feet per second, miles per hour

4. Let’s Try: A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast (what speed) were they running? S = d / t S = 100 m / 20 s S = 5 m/s

5. The pitcher’s mound in baseball is 85 m from the plate. The balls average speed is 21.25 m/s. How long does it take for a pitch to reach the plate? Let’s Try: t = d / s t = 85 m / 21.25 m/s t = 4 s

6. Now it’s time for the ANIMAL RACE

7. If something is not moving, a horizontal line is drawn on a distance-time graph Time is increasing to the right, but its distance does not change. It is STOPPED.

8. Both are CONSTANT SPEEDS. A steeper gradient = higher speed.

9. Can you describe what is happening here? CHANGING SPEED. For the first part of the journey, the object moved at a steady (slow) speed. It then suddenly increased its speed.

10. Can you describe what is happening here? CHANGING SPEED

11. Velocity: The speed of an object in a particular direction. An airplanes velocity is 600 km/h An airplanes velocity is 600 km/h SOUTH

12. An objects velocity is constant ONLY if its speed and direction don’t CHANGE

13. Which of the following are examples of velocity? a) 25 m/s forward b) 1,500 km/hr c) 55 m/h south d) All of the above Letters a and c are examples of velocity

14. Resultant Velocity: The combination of two or more velocities.

15. If you are riding a bus traveling east at 25 m/s. You stand up and walk down the bus’s aisle at 1 m/s east. What is your RESULTANT VELOCITY? 15 m/s east + 1 m/s east = 16 m/s east

16. If you are riding a bus traveling east at 25 m/s. You stand up and walk down the bus’s aisle at 1 m/s west. What is your RESULTANT VELOCITY? 15 m/s east - 1 m/s west = 14 m/s east

17. When velocities are in the same direction, add them together. When velocities are opposite direction, subtract them. *The resulting direction is from the larger velocity!

18. Acceleration: the rate at which velocity changes. Acceleration = final velocity – initial velocity time it takes to change velocity Units for acceleration: m/s 2

19. You are riding your bike down a hill. At point A your velocity is 5 m/s south. 2 seconds later you pass point B and your velocity is now 25 m/s. What is your acceleration from point A to point B? Acceleration = 25 m/s – 5 m/s 2 s Acceleration = 10 m/s 2

20. Acceleration = 0 m/s – 45 m/s 5 s Acceleration = -9 m/s 2 You are coming up to a stop sign and start to press on the breaks. 5 seconds from the sign, your velocity is 45 m/s west. Once you reach the sign you have stopped, your velocity is 0 m/s west. What is your acceleration as you approach the sign?

21. Can you describe what is happening here? Acceleration in which velocity increases: POSITIVE ACCELERATION Acceleration in which velocity decreases: NEGATIVE ACCELERATION

22. Can you describe what is happening here? Velocity stays the same: NO ACCELERATION (CONSTANT VELOCITY!)

23. Can you describe what is happening here? CHANGING ACCELERATION