## Friday, February 6, 2009

### Science Saturday Challenge #2

Pressure is force applied over an area, P = F/A. The larger the area, the less the force on each unit of area. In other words, the force is "spread out" across the whole area.

Materials:

4 balloons
1 small table or other long, flat area that kids can stand on

Procedure:

Inflate the balloons about half way, tie them off, and place them on the floor.

Turn the small table over and place it on the balloons.

Holding the table stady help your children stand in the center of the table.

Ds#1 knew right away that the balloons would not pop, though he thought it had more to do with the balloons not being directly under his weight.

They noticed how the balloons changed shape; I pointed out that all 4 balloons changed because the weight (force) in the center of the table created pressure in all 4 balloons and was, in fact, divided among the balloons. Also, the balloons spread out so that more area touched the table, which decreased the pressure on any one spot.

When you do it, put the balloons under the table a bit more, otherwise the corners of the table can dig into a balloon if a child does not step directly onto the center of the table. Ds#3 stepped up with ds#1 for a total combined weight of about 100 lbs. Ds#2 had a fever and only wanted to look on.

The standard unit of Pressure is 1 pascal (Pa) = 1 Newton/m² = kg/(m· s² ), named after Blaise Pascal, who invented the hydraulic press and the syringe, among other things. The Imperial equivalent is psi, or pounds per square inch.

You can also demonstrate this using straight pins. Tape graph paper to cardboard. Stick a pin through every corner. Place an inflated balloon on the pins and a brick on top of that. Just like the bed-of-nails trick!

L a u r a said...

The kids will enjoy this one. I first need to get some more balloons. We just used up our last balloons making a model of the lungs (from Blood & Guts).

Thanks for another practical lesson idea!

Cheryl said...

This looks like a cool experiment that the kids would really enjoy. You know turning furniture over and standing on it is a big thrill!

Hey Laura, We're doing the respiratory system this week too with plans to do some lung experiments. Gotta love that Blood and Guts!
Blessings,
Cheryl

julie said...

Great Experiment!!! It is so exciting to see real science at home rather than kids making paper mache' globes and calling it science. Kudos to you!!! Thanks for the link to our website. We really appreciate your support! If your children liked learning about Pascal, perhaps they will enjoy learning about Bernoulli as well. Here is one of my favorite experiments demonstrating Bernoulli's principle http://www.stevespanglerscience.com/experiment/00000037 Good Luck to you and your very lucky children!!

Kris said...

Laura--that was a great experiment, too. We'll be getting there soon enough in Blood and Guts

Cheryl--I'm thinking of doing that for the Hands On Science class for co-op. Can you assist in that class?

Julie--thank you so much! I will certainly check out Bernoulli. Your site is an outstanding source of information, so I am happy to support what you do.

J's mom said...

Thanks, we did this yesterday. It worked great!!!!

I found this site through Mater Amarabilis. Do you have a website for them?

Kris said...

The MA website is http://materamabilis.org/ma/intro/

I'm glad you had fun with it!