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SPEED Speed Speed is the distance an object moves in a particular amount of time. OR How far you go and how long it takes to get there. How to find the speed of an object or a person: Calculate Speed Distance /Time (distance divided by time) Try some: calculate the speed Distance -> Time 1m 2m 3m 4m 6m 1 hour 2 hours 3 hours * Answers Distance -> Divided by Time 1m 2m 3m 4m 6m 1 hour 1m/h 2m/h 3m/h 4m/h 6m/h 1m/h 1.5m/h 2m/h 3m/h 2 hours 0.5m/h 3 hours 0.33m/h 0.66m/h 1m/h 1.33m/h 2m/h * Average Speed Most objects do not move at constant speeds for very long. Race cars change speeds many times during the race: slower around the curves and faster on the straight places. Graphing Motion You can show the motion of an object on a line graph. Time is on the X-axis (horizontal) and distance is on the Y-axis (vertical). The 2 numbers are called coordinates of the point. Moving Man: http://www.mste.uiuc.edu/Murphy/MovingM an/MovingMan.html Graphing Constant Motion Constant motion is motion that does not change. That means the object is neither speeding up or slowing down. Constant motion is shown as a straight line on a graph: Motion: Constant Motion Motion: Constant Motion 12 20 Distance (m) Distance (m) 25 15 10 5 0 10 8 6 4 2 0 0 1 2 3 4 5 Time (min) 6 7 8 9 10 0 1 2 3 4 5 6 Time (min) 7 8 9 10 Constant Motion Graph The slope of the line can be used to determine the speed of the object. The change in distance for every minute on this graph is constant. Motion: Constant Motion 25 Distance (m) This graph shows constant motion because the slope of the line does not change. 20 15 10 5 0 0 1 2 3 4 5 6 7 8 9 10 Time (min) Speed = distance time In this graph Speed = 2 m/min. Constant Motion continued The slope of this line does not change either. The distance on this graph stays the same. Motion: Constant Motion 12 Distance (m) This graph also shows constant motion because the slope of the line does not change. 10 8 6 4 2 0 0 1 2 3 4 5 6 7 8 9 10 Time (min) Speed = d/t = 0/10 = 0 m/min So what can be said about the motion? The object is not moving. Change in Motion Change in motion can be seen as a change in the straight line or as a curved line. Motion: Change in Motion Distance (m) 25 20 15 10 5 0 0 1 2 3 4 5 6 7 8 9 10 7 8 9 10 Time (min) Motion: Change in Motion Distance (m) When looking at a graph, you can tell when motion changes because line is not straight. 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 Time (min) 6 Change in Motion continued Motion is constant between minutes 0 and 4, 4 and 6, and 6 and 10. Even though between these points motion is constant, the overall motion changes. Motion: Change in Motion 25 Distance (m) In this graph, there are three different types of constant motion. 20 15 10 5 0 0 1 2 3 4 5 6 Time (min) 7 8 9 10 Change in Motion continued Motion is constantly changing. The curve of this graph shows acceleration. Acceleration is the increase or decrease in speed. Motion: Change in Motion Distance (m) In this graph, the motion is not constant between any two points. 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 Time (min) This graph shows increasing speed because the curve goes upward. 10 Change in Direction By looking at the slopes of the two lines, what can be said about the speed before compared to the speed after turning around? Motion: Change in Direction 20 Distance (m) On a motion graph, you can tell when the object reverses direction because the distance from the starting point becomes less. 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 Time (min) The speed before turning around is quicker because the _______ is greater Slope than after turning around. Line graphs can show all kinds of information. Look at the axis labels before you analyze the information. Time Graph Connect the dots and analyze the graph 600 m race 4 3 3.5 3.5 3 3 3 3 Time (min) 2.5 2.5 George 2 Nina 1 0 Lap 1 Lap 2 Lap 3 Lap Lap 4 Analysis: Time Graph This is a graph showing time for 2 runners in the 600 m race. It shows that George ran 2.5 minutes for the first lap, 3 minutes for the 2nd lap, 3.5 minutes for the 3rd lap, and 3 minutes for the 4th lap. Nina ran 3 minutes for the 1st, 3.5 for the 2nd, 3 for the 3rd, and 2.5 for the 4th. To calculate the average speed, take the total distance and divide by the total time. George’s average speed: 50 m/min Nina’s average speed: 50 m/min