# 8th Gr Science Ch 18

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1. When is something in motion?
When it is changing position
2. What does "changing position" mean?
When an object moves from one location to another
3. 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
4. Define motion
Motion occurs when something changes position relative to a reference point
5. 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.
6. Can distance and displacement be equal?
Only if the object moves in a straight line
7. Define speed:
Speed = the distance an object travels in a unit of time
8. What is the equation for speed?
speed (in meters per second) = distance (in meters)/time (in secs) OR s = d/t
9. Speed can be calculated in units other than meters per second.
True
False
• True
• for example it can be calculated in kilometers per hour
10. What is instantaneous speed?
The speed of an object at one instant of time is the object's instantaneous speed
11. 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
12. 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
13. 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?
14. What do you use a distance time graph to compare?
You can use a distance time graph to compare the speed of objects.
 Author: carrieross ID: 46432 Card Set: 8th Gr Science Ch 18 Updated: 2010-11-01 11:38:15 Tags: motion Folders: Description: P 522-527 Glencoe 8th gr science:What is motion? Show Answers: