SPEED…

1. SPEED… So what all is involved?

2. So what is speed? • By definition, speed is a measure of how fast something moves or the distance an object moves in a given amount of time. • The greater the speed an object has the faster it changes position. • So what do we mean about position?

3. Position • The position of a place or object is the location of that place or object. • For example: The American Flag is located at the front of Mrs. Lancaster’s room directly over the chalkboard and to the left corner. • This gives the “position” of the flag.

4. Where are you? • We use something called a reference point to describe the position of a place or an object. • Reference points are used to compare other locations. • For example: We use latitude and longitude on maps to determine exactly where a certain location is and its relative position to another location.

5. So then, what is motion? • Motion is a change of position over time. • A change in the position of an object is evidence that motion has occurred. • For example: When a track athlete participates in the broad jump, you know that they are in motion due to the fact that they have changed positions from the starting point to the ending point.

6. Now…back to speed! • How can we determine the speed of an object? • First, we must find out the distance that the object has traveled. • Second, we determine the time it took that object to travel that distance. • Finally, we divide the distance by the time traveled, and there you go…the object’s speed!

7. Formula for Speed • Speed = distance time **Don’t forget you can place this formula in a triangle.

8. Units in calculating speed • For distance we normally use meters (m), but we also can use kilometers (km) and centimeters (cm) depending on the object. • For time we normally use seconds (s), but can also use hours (hr) depending upon the object. • Most equations will be measured in meters per second, or m/s.

9. Speed problems… • A man runs 200 m in 25 s. What is his speed? • If you travel 100 m in 50 s, what is your speed?

10. Answers… • Speed = distance time Speed = 200 m 25 s Speed = 8 m/s

11. Speed answers continued… • Speed = distance time Speed = 100 m 50 s Speed = 2 m/s

12. Then what is velocity? • Velocity is speed in a specific direction. • For example: My speed might be walking 3 m/s, but my velocity is walking 3 m/s east. • Velocity is considered a vector because it is a quantity that has both size and direction. Speed is NOT considered a vector as it only deals with a measure of how fast an object travels.

13. Acceleration • Acceleration is a measure of how quickly the velocity is changing. • Note: If velocity does not change, there is no acceleration. • Speeding up: acceleration in the same direction as motion • Slowing down: acceleration in the opposite direction of motion • Direction change: acceleration at a right angle to motion.

14. Calculating for Acceleration • Formula: Acceleration = final velocity – initial velocity time Or, A = vfinal – vinitial t So…can you do this?

15. Try this one… • Lou starts sliding with a velocity of 1 m/s. After 3 s, his velocity is 7 m/s. What is Lou’s acceleration? • Acceleration = final velocity – initial velocity time A = 7 m/s – 1 m/s 3 s A = 6 m/s 3 s A = 2 m/s2