For the Projects we’ve done so far we’ve accepted that the paper, the car, the balls and the jar moved. What is motion?
Look up motion in the dictionary. What does it say?
My dictionary says motion isthe act of changing place or moving.
We used vectors earlier to show the direction of a force. Vectors can also help us show where and how far something is moving.
Another concept in physics is displacement. This is how far something moves from its original position. This is not the same as the distance something moves.
Question: How can vectors show how something moves?
Sheets of Grid paper [quarter inch is fine]
Draw a line across a sheet of grid paper about ten squares from the top
The line is a street
Make a little mark across this line every second square
These marks show blocks
Draw a little house at the middle mark on the line
On a map east goes to the right, west to the left, north up and south down.
You leave the little house and walk three blocks east to the market
To show this draw a line from the mark in front of the house three blocks east or and put a little arrow at the end of the line.
Now you walk three blocks west back to the little house
Draw another line from the market to the little house and put a little arrow on the end
How far did you walk?
This is distance. Your total distance is 3 blocks east plus 3 blocks west or 6 blocks.
What is your displacement?
Notice on your graph the arrows are equal and opposite. The vectors say you did not go anywhere.
Displacement is how far something moves away from where it started. In this case the displacement is 0 because you started and ended at the same place.
Draw another line about ten squares below the first line and put a little mark in the middle
This time each square is a block
You go to a friend’s house five blocks west of your house
Draw this vector
The two of you decide to go to another friend’s house seven blocks east of where you are
Draw this vector
Later you and your first friend go to your homes for dinner
Draw these vectors
What distance did you walk?
What distance did your first friend walk?
What distance did your second friend walk?
What is your displacement at your first friend’s house?
What is your displacement at your second friend’s house?
What is your first friend’s displacement at your second friend’s house?
What is your total displacement?
What is your first friend’s total displacement?
Your lines and vectors
On Your Own
Draw another line about ten squares below your last vector line
Mark your home in the center
Walk the five blocks west to your friend’s house
[Hint: This may be easier if you use more than one color for the vectors such as one to you alone, one for you and your first friend, one for the three of you and one for your two friends.]
The two of you walk seven blocks east to your other friend’s house
The three of you go five blocks east to a park for the afternoon
The three of you go to your house for supper
Your two friends go back to your first friend’s house for the night
What distance did you go?
What was your displacement?
What distance did your first friend go?
What was your first friend’s displacement?
What distance did your second friend go?
What was your second friend’s displacement?
What I found Out:
I walked 5 blocks W + 7 blocks E + 5 blocks E + 7 blocks W or 24 blocks. My displacement was 0 because I started and ended at home.
My first friend walked 7 blocks E + 5 blocks E + 7 blocks W + 5 blocks W or 24 blocks. My first friend’s displacement is 0 because of starting and ending at home.
My second friend walked 5 blocks E + 7 blocks W + 5 blocks W or 17 blocks. My second friend’s displacement is 7 blocks because of starting at home and ending at my first friend’s house.