Dr. Joseph W. Howard ©Spring 2008 What is Motion? What is Motion? to moveWhat is “to move?” observe movedWhat do we need to “observe” to say something has indeed moved? not movingWhat is “not moving?” MOTIONHave you ever really thought about motion? It seems like a simple idea, simple observation, ……but let’s take a look at MOTION to moveWhat is “to move?” observe movedWhat do we need to “observe” to say something has indeed moved? not movingWhat is “not moving?” MOTIONHave you ever really thought about motion? It seems like a simple idea, simple observation, ……but let’s take a look at MOTION

Dr. Joseph W. Howard ©Spring 2008 Frame of Reference frame of reference Any measurement of position, distance, and/or speed (or really anything) MUST be made from a “frame of reference.” starting point A starting point origin An origin common location A common location A reference point to judge “change”

Dr. Joseph W. Howard ©Spring 2008 Distance? What is it? What do people usually mean by “distance?” Distance is the total length of travel that an object has moved. Is this enough?

Dr. Joseph W. Howard ©Spring 2008 Examples EastWest 1 m Distance = 4 m

Dr. Joseph W. Howard ©Spring 2008 Examples EastWest 1 m Distance = 8 meters

Dr. Joseph W. Howard ©Spring 2008 Examples EastWest 1 m Distance = 6 meters

Dr. Joseph W. Howard ©Spring 2008 Examples EastWest 1 m Distance = 4 m East 1 m Distance = 4 m We have a problem We have a problem Same distance, different location Same distance, different location

Dr. Joseph W. Howard ©Spring 2008 Examples EastWest 1 m Distance = 4 m Displacement: net change in location from a starting point that an object moves during the observation of that object. Displacement = 4 m West

Dr. Joseph W. Howard ©Spring 2008 Examples EastWest 1 m Distance = 8 meters Displacement = 0 meters

Dr. Joseph W. Howard ©Spring 2008 Examples EastWest 1 m Distance = 6 meters Displacement = 2 meters West

Dr. Joseph W. Howard ©Spring 2008 Examples EastWest 1 m Distance = 4 m East 1 m Distance = 4 m Displacement = 4 m West 2 m West

Dr. Joseph W. Howard ©Spring 2008 Displacement Displacement is the “net change” in location from the beginning location. Okay, so we are clear on the difference between “distance” and “displacement.” What’s next?

Dr. Joseph W. Howard ©Spring 2008 Notice how we represent “ amounts & directions !” We use “ arrows ” to indicate the amount and “ arrowheads ” to indicate direction. We call these VECTORS A displacement vector is an arrow whose length represents the net change in location for an object and the direction it moved. Vectors

Dr. Joseph W. Howard ©Spring 2008 Vectors 5m 2m8m Same distance different displacement Same direction, different displacement & distance Directions are very important in describing motion!! Directions are very important in describing motion!!

Dr. Joseph W. Howard ©Spring 2008 Vectors Vectors are especially useful when combining motions and when describing changes in motion. We will be using “vector arrows ” in many useful ways !