Section 1.2 Outline

Speed measures how fast position changes

I. Position can change at different rates

1) speed: a measure of how fast something moves

a) rate at which distance changes compared to time

b) a measurement; can be fast or slow

2) speed and position are related by time – speed measures how quickly position change

A. Calculating Speed

1) objects that travel at different speeds move different distances in the same amount of time

2) S = d/t (S = speed, d = distance, t = time)

B. Average Speed

1) speed is not constant; it is always changing

2) moment-to-moment speed (instantaneous) is difficult to measure

3) easiest to calculate average speed over a distance

C. Distance-Time Graphs

1) shows how speed relates to distance and time

2) shows how both distance and speed change with time

3) a flat, or horizontal, line shows a speed of 0 m/s

4) time is on horizontal, or x-axis and distance is on vertical, or y-axis

II. Velocity includes speed and direction

1) velocity: a speed in a specific direction

2) example: 3 m/s south

A. Velocity

1) to calculate, need both speed and direction

2) vector: a quantity that has both size and direction

3) represented by an arrow (size and direction)

B. Velocity versus speed

1) two objects may have same speed, but different velocities

2) average speed depends on total distance traveled

3) average velocity depends on total distance from starting point