Mechanical Energies November 16, 2010

In class, we were given whiteboards a

nd told to write the systems for the following situations:

1. A person is being dragged across a rug.

2. A hot air balloon rising up into the air.

3. Someone bouncing on a pogo stick.

4. A car going faster and faster.

The answers we came up with in our class discussion we

re:

#1 the system was the earth, person being dragged, and the rug.

#2 the system was the earth, hot air balloon.

#3 the system was the pogo stick.

#4 the system was the car.

Next we had to find the equation for work and what the negative signs means using the table

The equation is force * displacement = work

The negative sign means that you are applying a lot of opposite force.

After we did this we compared answers with two other groups. Our answers all agreed with each other.

Then we had to fill in this table.

Today in class I learned much more about systems because that was a topic that was a little confusing for me. I hope this blog helped teach you more about systems and mechanical energies.

-JM

November 12 2010 Period 2

First, in class we discussed on homework. We were given white boards. Each table was assigned a problem from the homework. Here is what we discussed in class.

The text in Red is the work done to the system

Group A- Someone Lifts Up a book- 10j+20j=30j



Group B-Pushing A Lawn Mower- 0j+5j=5j



Group C-A person Goes Bungy Jumping- 5j+20j= 25j



Group D-A car speeding down then going up a small ramp. Then it flies in the air- 40j+20j=60j



Finley-A person bouncing on a trampoline- 20j=20j No work



Group G- A rock climber starts falling down and his hands burn on the rope. 20j=20j No work


That took up all of class. A good link that I found to help. Use it if you are unclear about something
I hope the Blog helped.

ZK

Today at the beggining of class, Finley asked us to get out our homework from monday and soon proceded to ask us what we thought Potential Energy was. After talking in our groups, Finley asked us what potential meant and the answer was when someone or something has the power to do something. We then went back to our chalk smashing ability experiment and said when I lifted the book I gave it potential energy. We then started on a summary and then proceeded to answer questions about postive work process. After we went on to share our answers. The type of energy we would get is Internal Energy because of friction. We concluded that if the surface that the crate was dragged on no friction being created so to creat energy we need the surface. A good link is
http://jersey.uoregon.edu/vlab/PotentialEnergy/

Monday, November 08, 2010

First, our tables created a whiteboard filled with information on Energy.






One of the concepts Mr. Finley reminded us about was that, "Energy cannot be created, energy can only be transferred."

Types of Energy
Mechanical Energy- ex. chalk smashing ability or CSA
Light Energy- see information from the light unit
Chemical Energy- ex. Battery
Electric Energy- Electricity
Nuclear Energy

Changes In Energy
Lamp- Electric Energy to Light Energy
Battery, wire, and light bulb- Chemical Energy to Electric Energy to Light Energy

Our Main Focus On Energy This Unit: MECHANICAL ENERGY

Why was today's class important? Any confusion with anything? Advice?
The first important thing we did was review. Reviewing is very important. It helps us remember concepts that we may have forgotten in the past. It also helps clear up any confusion anyone may have concerning any topic.
Then, Mr. Finley talked about types of energy. This helped us understand what types of energy there were. He also said we would be focusing on Mechanical Energy. This would help us understand what we are learning.
Lastly, Mr. Finley told us to think of some situations where energy changes. This was important because it helped us understand that there are many situations when there are changes in the type of energy. The ones listed above are only a few very simple ones. Below are a few more.

-YZ

November 3, 2010

First, Finley checked our homework. He went around as usual to make sure everyone did it. Then, he called up four people to go up on the board and draw what they got.





1) 0J + 20J = 20J


2) 0J + 50J = 50J


3) 40J + -40J = 0J


4) 5J = 5J

Then we played a review game to review for the test.

Chalk Smashing Ability

We first reviewed from yesterday. We discussed that we needed a push or pull in other words a force. We also said that the directoin of the force and displacement had to be going in the same direction to have CSA (chalf smashing abilities).

Why does it matter to talk about both diplacement and force?

We said that it was both important because even if we give some things force it may not be able to be diplaced.

Ex. Yuji tried to push the table fixed to the ground. It didn't move and couldn't get CSA

Finley then forced the dictionary up but he diplaced the object sideways. The dictionary did not get CSA.

We then disucussed what happened with me pushing the desk and Finley displacing and forcing in a different direction.

For me pushing the table I couldn't diplace it because it was fixed to the floor. For the dictionary going in different directions the force and displacement was going in different ways so the dictionary could not get CSA.

We then experimented with this theory. We had Hleb as the chalk smashing machine and Daphnie was part of the Chalk Liberation Movement. Hleb pushed the cart at the chalk and Daphnie pushed the opposite direction to save it.

Here is the results

Hleb: 10 units of CSA

Daphne:-10 units of CSA

Daphne + Hleb: 0 units of CSA

So expressed as a number sentence 10-10=0
Yay! Daphnie saved the chalk!

We then did this again with Finley and Hleb and this time because Finley did not push as hard to stop the displacement the cart still got CSA. We now had to revisit the first hypothesis that force and displacement had to go the same way for a object to got CSA.

This is what we came up with.

New Hypothesis: When the force and displacement is going the same direction increases the CSA. When the displacement and force are going opposite directions the CSA decreases.

Finley then gave us another puzzling question.
Where did the CSA come from?

A good guess was that it came living things. This was disproved when Finley pushed a cart into another cart and gave it CSA. The cart had given the cart CSA.

We concluded that it came from a external source of energy.

We then defined work.
Work- when we transfer energy to or from another object or system.
We can either do positive or negative work on the system.
Ex. Daphnie did negative work to the cart when it was trying to gain CSA.

We then discussed what was initial state and final state.
Initial state: where it started
Final state: where it ended up after the work

Ex. Finley lifts book
Initial state: Sitting on table
Final state: In the air in Finley's hand

We now set about to try to show how much energy the book had and got after it was lifted.
We said that the book already had 10 units of energy. After it was picked up it had 30 units of energy. Finley had to do 20 units of work in order to achieve this.

HW: Look on Finley's website

YS

its NOVEMBER!!!!! wow! (chalk smashing experiments)

11/1/10

As always, we checked the homework from over the weekend. Homework from October 27 to now. we were going to play a review game, but our questions were not to good. we weren't as creative as he wanted us to be. so, no review game.

we started talking about why we see a rainbow in white light. the speeds of the light are different. the ones that bent the most will be moving the slowest. the wave length would be the smallest.

why doesn't this happen with lasers? it is ONE focused wave length.
where else do we see this happening? rain... a rainbow... the light goes through a refracts at an angle off the humidity in the air. that creates a rainbow.

any questions about the dissection on Friday? Kevin- what was the blob jello stuff... answer-fluid that refracts the light.

ELECTRO MAGNETISM

forms of energy- x rays, microwaves...

Conner volunteered to pick up a dictionary and smash the piece of chalk on it. he put the book higher and dropped it onto the piece of chalk.. it got crushed...

displacement- moved, changed position by some amount
what is the direction that the book was placed in order to smash the chalk.. the book went up... Conner's force was up... so our displacement was up and the force of Conner was up. so as a result the book gained chalk smashing ability.

we did another observation
now we want to give the cart chalk smashing ability. chalk is now taped to the wall and molly has to push the cart towards the wall. and try to smash the chalk.

try 1- the wheels stick out too far and the cart cant touch the chalk.. now we have an assumption that we have to work through.

try 2- we taped the chalk to a brick taped to the door and molly tried it again and it worked.. the cart has smashing ability

(force = push or pull)

the bell rang and as usual we are late trying to finish up our class hopefully tomorrow we will try to finish up our experiments on the force and chalk smashing. - G.P.