| A | B |
|---|
| What is needed to describe motion completely? | a frame of reference |
| frame of reference | a system of objects that are not moving with respect to one another |
| relative motion | movement in relation to a frame of reference. For example, as a train moves past a platform, people on the platform will see those on the train speeding by, but to another person sitting across from the person on the train, that person is not moving at all. |
| distance | is the length of the PATH between two points |
| standard unit for measuring distance | meter |
| unit for measuring long distances | kilometer |
| unit for very small distances | centimeters |
| displacement | the direction from the starting point and the length of the straight line from the starting point to the ending point |
| displacement is an example of a | vector |
| vector | a quantity that has magnitude and direction. The magnitude can be size, length, or amount. Arrows on a graph or map are used to represent this. |
| resultant vector | the vector sum of two or more vectors |
| Is displacement more like the length of a rope pulled tight or the length of a coiled rope | the length of a rope pulled tight because displacement measures a straight line from the starting to ending point |
| speed | is the ratio of the distance an object moves to the amount of time the object moves |
| average speed | is computed for the entire duration of a trip. It is the total distance traveled divided by the time to travel that distance |
| instantaneous speed | is measured at a particular instant |
| velocity | a description of both speed and direction of motion. It is a vector. |
