| What is Motion? Section 1-2: Measuring Motion |
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| A. A change in position in a certain amount of time is motion. 1. When you describe motion, you are comparing it with a frame of reference. B. Motion can be measured when you know the distance, and the time therefore you are actually calculating speed. 1. Speed (S) is the rate at which an object moves. 2. Distance (d) is measured in miles or kilometers 3. Time (t) is measured in seconds or hours 4. Unit of Speed is meters / second (m/sec) Formula: SPEED = DISTANCE / TIME C. When speed does not change it is called constant speed which means the speed is the same at every point in its path 1. Distance - Time graph for constant speed is shown with a staight line. D. Average speed is speed that is not the same at every point on its path. 1. A distance - time graph for average speed will be a line that is not straight. 2. Most things change speeds many times during the time and distance it travels, which makes average speed a common thing. E. Velocity is speed in a given direction. 1. Combined velocities occur when you are moving and so is the object under you. 2. When two things that are moving in the same direction, the speed / velocity are added together. 3. When two things are moving in the opposite direction, the speed / velocities are subtracted. |
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