## Wednesday, March 2, 2011

### New Unit - Astronomy

Today we are starting a new unit - Astronomy

We started off class with a demonstration of holding a bowling ball in one hand and a ping pong ball in the other. Then we observed what happened.

• You have to push up to hold each ball

• There is a different push on both sides because of the weight difference

We then discussed a new term, force, and that you are applying force to the ball to hold it.
Force - Interaction between 2 or more objects. (push, pull, etc.)

"The student had to have done work to the ball in order to hold it up." This is not true because you are applying force to the ball, not work. The ball has gravitational potential energy when it's being held, but nothing is doing work to it.

QuEsTiOnS

+What would happen is this was the only force exerting the bowling ball?

-The only force is pushing up, so it would keep going up and not come down

+Are there any other objects exerting a force?

-The earth is pushing the ball down.

There is an equal amount of force on both sides so it is balanced.
Our number statement for this scenario would be: +7 + -7 = 0

This is because you are giving the ball energy when you hold it above the ground. The earth is pushing down on the ball, making it lose its energy.

During class today, someone mentioned something about the displacement of the ball. I didn't really understand that and why it was displacement. Could anyone tell me about it?

EE (3rd blog)