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
Direction Convention Positive Negative
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
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.
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.
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
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.
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.
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.
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.
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.
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)