Describing Motion with Graphs

1. Describing Motion with Graphs

2. Describing Motion with Position vs. Time Graphs Position is plotted along the y-axis Time is plotted along the x-axis Slope on a position vs time graph equals average velocity Slope = y2 – y1 = Δx = Vavg x2 – x1Δt

3. Consider a car moving with constant velocity to the right. (+10m/s) A graph of the motion would look like this: Note that a motion described as a constant, positive velocity results in a line of constant and positive slope when plotted as a position-time graph.

4. Now, consider a car moving with changing velocity to the right. The speed is increasing. A graph of the motion would look like this: Note that a motion described as a changing, positive velocity results in a line of changing and positive slope when plotted as a position-time graph.

5. Constant Positive Velocity (moving right, constant speed) Changing Positive Velocity (moving right, increasing speed)

6. moving right moving right constant velocity constant velocity slow fast moving left fast moving left slow constant velocity constant velocity

7. position position time time Curved lines have changing slope – object is accelerating. Is it getting faster or slower? In what direction is it moving? slope starts out low, ends steeply slope starts out steep, ends flat increasing speed, right decreasing speed, right