Homework for tonight: Read p. 76-80; work problems #1-7 on p. 80. #4 can have some different answers, and you will use one of the equations that we found in class today to solve #6&7. Show your work with units!
**If anyone is successfully using the online or CD version of the textbook and doesn't need their paper one anymore, please bring it in; I have 2 students who have no computers and no books either.**
Also in class today: Described motions that were represented by sketches of position - time graphs and velocity-time graphs. You'll see more of these tomorrow and next week.
Today after our warm-up and after correcting people's homework (plotting graphs), we calculated slopes and equations for the lines you plotted last night.
Our position - time graph showed us a curve: changing slope, which indicated changing speed (cm/s was the unit for that line's slope). A line drawn between two points on this graph shows delta x over t, or average velocity over that time period. (you already have that equation in your notes)
The position - time^2 graph shows the same data, but it looked straight. This we could work with: we calculated its slope and gave an equation for the line. We got a new (weird) unit of cm/s^2 by taking delta x / t^2. Later we found this value to be 1/2 of acceleration and made a new equation for the line:
delta x = 1/2 a t^2
The velocity - time graph's slope shows how much velocity changes per second, also with that weird unit of cm/s^2. The slope of this line gave us another new equation;
a = delta v / t
Tomorrow we'll have more practice and hopefully a practical measurement of an object that accelerates as well.
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