2. Distance, Displacement Speed, and Velocity

3. Frame of Reference - In order to measure the distance of an object we must use a frame of reference. Point A --------> Point B - These are usually distinct points on the Earth's surface or distinguishing points in the sky.

4. The perception of motion depends on the observer’s frame of reference Describe the motion observed by one of the boys in the drawing, how does the motion appear to be different to the other boy?

5. The perception of motion depends on the observer’s frame of reference Imagine you are the girl observing the bus, describe the motion of each object that you can see

6. Distance is a scalar quantity and tells you only the magnitude (number sum only) of a path taken. scalar quantity = An amount or measurement that is not related to direction. Speed, volume, and temperature are scalar quantities.

7. Displacement is the shortest distance between the starting point and the end point.

8. Distance vs. Displacement You drive the path, and your odometer goes up by 8 miles (your distance). Your displacement is the shorter directed distance from start to stop (yellow arrow). What if you drove in a circle? start stop

10. From Home travel: 13 blocks East 6 blocks North 16 blocks West 6 blocks South What is your total distance? What is your total displacement?

11. Example 1: Example 1: An object moves from A (start) to D (end) along the red path as shown below. (Each square is 1 km) a) Find the total distance covered by the object b) Find the displacement of the object Total distance is 9 km Total displacement is 5 km

12. Example 2 An object moves, along a line, from point A to B to C and then back to B again as shown in the figure below. a) Find the distance covered by the moving object. b) Find the magnitude of the displacement of the object. Total distance is 13 km Total displacement is 5 km

15. Constant speed A moving object that doesn’t change it’s speed travels at constant speed A moving object that doesn’t change it’s speed travels at constant speed Constant speed means equal distances are covered in an equal amount of time Constant speed means equal distances are covered in an equal amount of time

16. Calculating Speed Speed = Distance Time If a runner travels 100 m in 10 seconds what was his average speed? Probably not constant Can solve for the other pieces too Distance = speed x time Time = Distance Speed

21. Calculating Speed Speed = Distance Time Can solve for the other pieces too Distance = speed x time T x S = D x T so D=T x S T 1 Time = Distance Speed Tips: 1. to move something to the other side, just do the opposite math operation to it. 2. If you do it to one side, do it to the other.

23. Motion When an object changes its position, motion has occurred. –Distance- How far an object has moved. –Displacement- How far an object has moved in relation to its starting point. –Consider direction Example: Two runners travel along the same straight path in a straight line for 500 meters. At the end of the run their distances are the same but their displacements are different. How can this be so?

24. Speed- Distance an object travels per unit of time Relationships between speed, distance, and time: Speed = Distance/ Time = d/ t »Constant Speed- speed does not change over time »Average Speed- speed of motion when speed is changing Avg Speed = Total Distance/ Total Time »Instantaneous Speed- speed at any given moment in time (speedometer)

25. Graphing Motion Graph distance on the y- axis and time on the x-axis Slope = rise = distance = speed run time run time

26. Distance - Time Graph If something is not moving, a horizontal line is drawn. If something starts out slow and then speeds up, its change in speed can look like this.

27. Learning Checkpoint This graph shows several stages of motion: Stage 1: 100 m in 10 s Stage 2: 50 m in 10 sStage 2: 50 m in 10 s Stage 3: 150 m in 20 s Calculate the speed as indicated by each of the colors. Calculate the average speed. What is the total distance? What is the displacement?

28. Solution Stage 1: S= d/ t 100 m/ 10 s= 10 m/s Stage 2: S= d/t 50 m/ 10 s= 5 m/s Stage 3: S= d/t 150 m/ 20 s= 7.5 m/s Ave Speed= Tot d/ Tot t 300 m/ 40 s= 7.5 m/s Distance = 300 meters Displacement = 0 meters

30. More Speed Practice

34. instantaneous velocity - the velocity that something has at any one instance –(The terms instantaneous speed and avg. speed may also be used)

35. Velocity The speed and direction of an object’s motion. –88 km / hr southwest

36. The average velocity for a trip might be 53 miles/hour. However, during this trip your instantaneous speed might have been 0 miles/hour at a stoplight or 70 miles/hour on the open road.

37. Video & Summarizer Highlight important facts on your Cornell notes paper. Study Guide They might be giants – speed and velocity video Group Work:Group Work: 1.Bubble Gum Physics Lab 2.Distance, Time, Speed practice problem worksheet.