Position and Displacement

Transcription

1 Position and Displacement Ch. in your text book Objectives Students will be able to: ) Explain the difference between a scalar and a vector quantity ) Explain the difference between total distance traveled and displacement ) Determine displacement of an object based on a position vs. time graph ) Describe, in words, the movement of an object based on a position vs. time graph

2 Direction Convention Positive Negative

3 Scalar vs. Vector Quantities Scalar quantity something that has a magnitude, an amount, but no direction Examples: mass, volume Check for understanding # Talk to your partner and make a list of three other quantities that you think could be classified as scalars. Vector quantity something that has a magnitude and a direction

4 Total Distance Total distance covered is how far you go, regardless of which direction you traveled. Check for understanding # If you go miles north, then miles east, then miles south. How far did you go? This is a scalar; there is only a magnitude. Example: The odometer on a car measures how far the car goes and it only counts up.

5 Displacement Displacement is the difference between where you ended up and where you started and it doesn t matter where you went in between. Check for understanding # If you go miles north, then miles east, then miles south. What was your displacement? Displacement is a vector. It not only has a magnitude, but also a direction. With vectors, a negative sign doesn t necessarily mean less, it could just signal which way an object is going.

6 Displacement Displacement is the difference between where you ended up and where you started and it doesn t matter where you went in between. Check for understanding # If object A has a displacement of m and object B has a displacement of -7 m, which is farther away from the starting point? What could you use to show the location of a person over a given period of time? Hint: you use them in math class all the time

7 Position vs. Time Graphs position (m) Vertical axis is for position; the unit is usually meters (m) Horizontal axis is for time; the unit is usually seconds (s) x (m) Sometimes they ll look like this time (s) t (s) Note: The graph does not say if the object is moving up or down, it only tells positive and negative movements.

8 Position vs. Time Graphs t (s) x (m) 0 Based on the data table, make a position vs. time graph in your notes. position (m) time (s) Note: The graph does not say if the object is moving up or down, it only tells positive and negative movements.

9 t (s) x (m) 0 Position vs. Time Graphs x (m) No arrow at the end of the line (you didn t run forever) The unit is next to the variable, not next to each number t (s) Note: The graph does not say if the object is moving up or down, it only tells positive and negative movements.

10 x (m) Position vs. Time Graphs t (s) Check for understanding Based on the graph, describe, in words, the motion of this person. Check for understanding What was the person s total distance traveled and what was their displacement? Note: The graph does not say if the object is moving up or down, it only tells positive and negative movements.

11 x (m) Position vs. Time Graphs t (s) Check for understanding Based on the graph, describe, in words, the motion of this person. Check for understanding What was the person s total distance traveled and what was their displacement? Note: The graph does not say if the object is moving up or down, it only tells positive and negative movements.

12 To Finish Up In your notes, answer the following questions: ) Explain the difference between a scalar and a vector quantity ) Explain the difference between total distance traveled and displacement ) Determine displacement of an object based on the position vs. time graph to the right ) Describe, in words, the movement of an object based on the position vs. time graph to the right x (m) t (s)