You CAN change the world

Never doubt that a small group of thoughtful, committed, citizens can change the world. Indeed, it is the only thing that ever has.

--Margaret Mead

Boy, 7, raises $240,000 for Haitian Relief.

Tonight's (1/25/10) Homework

Hey guys, I was having a little bit of trouble with 2c (see how Kinetic Energy vs. Distance Fallen graph and Gravitational Force vs. Distance Fallen graph help to define Gravitational Potential Energy). I feel like Gravitational Force and Gravitational Potential Energy are kind of the same thing... I'm kind of confused about the difference between the two/the 2c question in general if you couldn't tell already. Anything would help, please comment! Thanks so much!

Hard problem 3

Hard problem 2 is dead——if you helped solve it, be sure to claim your propsicle.

Hard problem 3 can be found here.

An important point about 5C

A very important point came up today when a few students were discussing 5c. The question was which of the following two graphs is the right answer. It turns out the bottom graph is right. Why?

Hard problem, still not quite solved...

It's begging for you to finish it off... Have mercy...

Hard problem

Big Ideas from 1/20

We discovered big understandings from force vs. displacement graphs and energy vs. position graphs. The area in a force vs. displacement graph is work. The work done by the spring force is - 1/2(k) (change in x)^2.
Energy depends on displacement, and a large displacement leads to a large energy. A small displacement leads to a small energy. For the kinetic energy vs. displacement graph, the total energy was constant. The difference between the total energy and the kinetic energy is the potential gravitational energy.

Class on Friday Jan. 15th

In class on Friday we talked about how to go about solving energy problems. Mr. Burk gave us some steps:

Guidelines For Energy Problems

1) Start by defining a system

2) Give symbols meaning (ex: instead of looking at a symbol like K and thinking of it as just K, think of it as change in kinetic energy)

3) Do everything symbolically

Also in class, we talked about power.

Also,

Power is measured in Joules per second or Watts. 1 Joule per second=1 Watt

Homwork is to finish 5C

Monday's scribe is... Jason