1. Linear Motion: Speed and Velocity

2. Speed It measures how fast an object is moving from one point to another It is a scalar quantity because magnitude is important but no direction is indicated

3. Velocity It measures the speed that an object is moving from one point to another in a specific direction It is a vector quantity because both magnitude and direction are important Standard SI units for speed and velocity are meters per second (m/s)

4. Formula for calculating average velocity:

5. Ex: Calculate the average velocity for a car that drove 825 m south in 137 s. v = Δx/Δt v = 825 m /137 s v = 6.02 m/s south

6. Calculating Instantaneous Velocity It can be calculated by using the exact time and location for one specific moment in time Ex: Calculate the instantaneous velocity at 25 seconds. v = x/t v = 20 m ÷ 25 s v =.8 m/s

7. Ticker Tape Motion Diagrams Use the diagrams to determine when the velocity is least and greatest. Remember, v = Δx/Δt * Note: A ticker tape is a long piece of paper attached to a moving object and threaded through a device that places a tick upon the tape at regular intervals of time - say every 0.05 second. As the object moves, it drags the tape through the "ticker," thus leaving a trail of dots. The trail of dots provides a history of the object's motion and therefore a representation of the object's motion.

8. Vector Motion Diagrams You can also determine an objects movement using vector diagrams; the magnitude of a vector quantity is represented by the size of the vector arrow

9. Practice Problems 1. Joe takes 9420 s to walk eastward along a straight road to a store 3000 m away. What is his average velocity?

10. Answer: v = Δx/Δt v = 3000 m /9420 s v =.3 m/s eastward

11. 2. Sue drives her car with an average velocity of 24 m/s towards the east. How long will it take her to drive 5.6 x 10 5 m on a perfectly straight highway?

12. Answer: v = Δx/Δt Rearranged to Δt = Δx/v Δt = 5.6 x 10 5 m ÷ 24 m/s Δt = 2.3 x 10 4 seconds

13. 3. Eugene is 75 km due south of Salem. If Bob rides from Salem to Eugene on his bike in 6 hr, what is his average velocity in m/s?

14. Answer: v = Δx/Δt v = 75 km ÷ 6 hr v = 12.5 km/hr But, we need the answer in m/s 12.5 km/hr · (1000m/1km) · (1 hr/3600s) v = 3 m/s south

15. Describing Velocity with Graphs Describing Velocity with Graphs A position vs. time graph will be used to show the velocity of an object Time is always on x-axis Time (s) Position (m)

16. Constant Velocity

17. Changing Velocity Changing Velocity (Acceleration)

18. Slow vs. Fast Velocity Slow, Rightward(+) Constant Velocity Fast, Rightward(+) Constant Velocity

19. No Movement There was constant velocity until the object reached 25 meters, then it stopped moving. No movement can be indicated by a horizontal line.

20. Practice Problems: 1.A car is moving with uniform velocity of 20 m/s north along a straight path. What is the distance covered by the car in meters after 10 minutes? 2.A person is riding their bike down the street at 13 km/hr. They see a pothole 8 meters ahead and needs to brake. How long in seconds does the biker have to react before he hits the pothole?