10-18

hmwk: p.111#1-8. 
Today we discussed why astronauts "float" - they ARE falling toward Earth, but as they fall, they're moving to the side so fast that the Earth's curved surface drops out beneath them (ORBIT!), and they continually accelerate around the Earth, constantly changing direction, forever.  As long as they don't speed up or slow down, they will remain at the same altitude forever. 
In reality the international space station does need to be boosted occasionally; it does encounter *some* friction from *some* atoms or molecules of air as it moves by, slowing it down, and decreasing its altitude. 
Most satellites are higher in altitude, and many are geosynchronous; meaning they remain over one spot on the Earth's surface permanently.  (this is achieved at a specific altitude and velocity).  Your satellite dish may be "aimed" at the satellite just when it's installed and point at that satellite forever, and our GPS satellites must have a very predictable location relative to the Earth's surface in order to work.
On the same lines of thought, if the Earth were to stop revolving about the Sun, it would fall in to the Sun, accelerating like a brick falling out of the sky.  When we get to more astronomy topics and math, we'll see how long it would take for the Earth to hit the Sun if this were to happen.  A real example is that the Moon is speeding up, and as a result, it is getting farther from the Earth by about 3cm per year. 

After the gravity - weight and orbit discussion, classes filled out note cards to use to keep equations and to use on any future test.  I also explained the algebra triangle, and how you could use it as a tool to help if you are struggling with Algebra and equations in class.  It will not be a tool that you can use on everything, and I won't give you the triangles for future equations.  It will be up to you to use them appropriately if you want.