# 8th Gr Science Ch 18

 When is something in motion? When it is changing position What does "changing position" mean? When an object moves from one location to another How do you know if an object has changed position? An object changes position if it moves relative to a reference point.eg. Starting the 100m dash behind the starting line then your position changes by 100m at race's end Define motion Motion occurs when something changes position relative to a reference point What is the difference between distance and displacememnt? Distance = distance traveled eg. the length of a route Displacement = the direction and difference in position between your starting and ending points. Can distance and displacement be equal? Only if the object moves in a straight line Define speed: Speed = the distance an object travels in a unit of time What is the equation for speed? speed (in meters per second) = distance (in meters)/time (in secs) OR s = d/t Speed can be calculated in units other than meters per second. True False Truefor example it can be calculated in kilometers per hour What is instantaneous speed? The speed of an object at one instant of time is the object's instantaneous speed What kind of graph do you use to represent the motion of an object? A distance time graph can be used to represent the motion of an object What do you put on the Y axis of a distance time graph representing the motion of an object? Distance is plotted on the Y or vertical axis What do you put on the X axis of a distance time graph representing the motion of an object? Time is plotted on the X or horizontal axis of a distance time graph representing the motion of an object? What do you use a distance time graph to compare? You can use a distance time graph to compare the speed of objects. Authorcarrieross ID46432 Card Set8th Gr Science Ch 18 DescriptionP 522-527 Glencoe 8th gr science:What is motion? Updated2010-11-01T11:38:15Z Show Answers