Tuesday Teaching {Hovercrafts}

There were certain concepts that were always met with a groan when introduced in class. Maybe this was because the concepts were taught them over and over again and they were certain nothing exciting was coming out of the lesson that day. Which made me want even more to find and create awesome projects to demonstrate the science principles!

One such principle was Newton's 3rd law - Every action has an opposite and equal reaction. 

A common example of this is letting the air out of a blown-up balloon. As you let the air out to your left, for example, an equal force pushes in the opposite direction (into the balloon) and causes the balloon to propel to the right.

Using this same concept, we can harness that equal and opposite force to create a simple and quick hovercraft.

With that brief introduduction, I'm sending you over to Scientific American to create such a hovercraft. Let me know your results! 

Click here!

Tuesday Teaching {Tightrope Walker}

Project: Tightrope walker 

Concept: Center of Balance

I was excited to find a couple emails last week from family wanting to know the science behind some interesting phenomenons. Which inspired me to think of how much more fun this would be for your kids if they were experimenting with their very own questions. So find out your kid's questions and let me know through the 'Ask Mrs. V' button on the sidebar ---------------------->

Thanks all!

One of the questions last week was:

Why do tightrope walkers carry those long poles?

This question may or may not have been spurred on by the recent feat of Nik Wallenda crossing the Niagara Falls. I only found out about this yesterday, but after reading how many viewers this attracted, I'm sure I'm the only one to not know about this.

Source here

He crossed the Niagara Falls in less than an hour. And yes, he did carry one of those long poles. But why?

This relates to center of gravity. Remember when we made the Balancing Bird? The bird would not balance because the center of gravity was not directly over the fingertip, or balance point. We needed to adjust the 'weight' of the bird so that the center of the 'weight' was at a point directly above the fingertip. 

A tightrope walker changes his center of mass by adding a pole. 

Stand up with your feet together and have someone gently (gently, brothers! :) try to push you over. It's pretty easy, right? 

Now stand with your feet spread apart and have someone gently try to push you over. That is harder to do. Even if you were to push harder than before, you would probably not be able to push them over. 

When you are standing straight up, your center of gravity, or middle of the 'weight', is more or less your stomach. When your feet are spread apart, your center of gravity is lower than it was before. When your center of gravity is lower, you are more stable because you are closer to the balancing point.

A tightrope walker on a thin wire is not able to spread his feet apart, but they CAN lower their center of gravity by holding a drooping pole with a little weight on either end.

Find a thin sidewalk to set up your own tightrope walk and grab a broom (with the end off) to test your skills!

Also, check out this balancing experiment for your project today:

http://www.stevespanglerscience.com/experiment/balancing-forks

Tuesday Teaching {Soap Fest}

Project: Soap Fest

 

Materials needed. Half & Half is used here as substitute for Whole Milk. Use whole milk if you have it! Use any flat tray you have - a cookie sheet works great too.

Pour enough half & half/whole milk to create a thin layer on the bottom of the tray. Use a few different food colorings and make 6-8 drops anywhere in the tray.

Pour drops of dish soap onto the food coloring. If you're quick, try to hit multiple spots of food coloring!

The initial spread is the most exciting. But continue to watch the dish soap drop and you will notice food coloring fizzing out of that circle for much longer!

When the reaction stops, mix the colors for some fun. Wash tray in the sink when finished - DO NOT DRINK.

Why does this happen? Let's think about Dish Soap. How does this liquid keep our dishes clean? More or less, it breaks down the fat molecules in food. Whole milk has.. lots of fat molecules. Try with reduced fat milk and you will see that this experiment doesn't really work.

As we pour the dish soap into the milk, the dish soap begins to break up the fat molecules in the milk. The food coloring doesn't add to the reaction, but allows us to see the reaction take place. 

Experiment! Does the size of the tray matter? Are there dish soaps that do a better job than others?

Thursday Teaching {Flight}

 Project: Airplane Wings & Ailerons

Concept: Flight

 I actually want to get to two concepts today. The first involves pressure and how an airplane wing helps an airplane to fly. This can get a little complicated, so I'll just leave a simple explanation and experiment. If your kids aren't quite ready for that yet, skip on ahead to the Airplane Ailerons experiment. Enjoy!

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We know how an airplane is able to fly thanks to our good friend Daniel Bernoulli, who discovered a fact known fittingly as the Bernoulli principle.

Wikipedia says: The Bernoulli principle can be used to calculate the lift force on an airfoil if the behaviour of the fluid flow in the vicinity of the foil is known. For example, if the air flowing past the top surface of an aircraft wing is moving faster than the air flowing past the bottom surface, then Bernoulli's principle implies that the pressure on the surfaces of the wing will be lower above than below. 

I say: The pressure of a moving gas decreases as its speed increases.

Because the shape of an airplane wing causes the air to move faster above than below, there is lower pressure above the wing. Higher pressure underneath the wing pushes the wing up and produces lift.

 

You can test the Bernoulli principle using a business card and a match. Adults, always be the one in charge of the matches. This experiment really is a 2-person deal, so I'll have to wait until the husband comes home to show you pictures. But, you don't have to wait - try it now!

 

Hold a business card in front of your mouth with a lit candle on the other side of the business card. 

Blow hard onto the business card. What happens to the flame of the match? 

... It moves toward you, toward the business card!

This is because you are creating a moving gas between your mouth and the card. Because air is moving quickly, you are creating a lower pressure. 

There is no moving gas between the card and the match. Air is moving slowly, creating a higher pressure.

 The higher pressure pushes the flame toward the area of lower pressure.

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This second experiment comes from the book Potentially Catastrophic Science by Sean Connelly.

There are a few different 'flaps' on an airplane wing that control how the airplane is going to move. An aileron is one such 'flap'. Ailerons on a wing control the rolling of the airplane. 

Picture yourself in an airplane. The airplane turns left. Easy, right? Well, the airplane doesn't turn exactly like a car turns. First, you tilt a little to the left (or roll a little to the left) before you turn. Can you imagine that feeling of rolling a bit before turning? Ailerons control that rolling.

In this experiment, you will create 4 identical airplanes. However, each airplane will have a different aileron configuration. Below are paper airplane instructions if you need them.

Fold your 'flaps' (ailerons) to match the above planes and let them fly!

You should have the following results: 

* One will fly nose-up towards the ceiling before falling

* One will nose-dive into the ground

* One will perfectly spiral to the left

* One will perfectly spiral to the right

What did you learn?

For really cool paper airplane designs, check out these websites. Your kids will love them!

http://www.funpaperairplanes.com/

http://www.amazingpaperairplanes.com/Simple.html

 http://www.paperairplanes.co.uk/planes.php

Monday Musings {Space Balloon}

This last week has been quite the busy one, but nothing really in the realm of 'Anything Else Fridays'. Just lots of family and celebrations. Sorry folks - this Friday there will be something here, even if the post is pictures of unpacked suitcases. You can't wait, can you! :)

This week, I want to switch gears from the sea to the sky. And as Mondays aren't really lessons, but tech/science thoughts or videos or inventions, I'm sharing the following incredible experiment:

If 6 minutes isn't too long for your child, definitely watch - it is worth it! A father and son team decide to send a camera into space - using an iphone and weather balloon. After months of research and experimenting, they set a date and come out successful, catching amazing footage and retrieving the balloon.

Although this kind of project requires money and probably a background in science/engineering, a motivating part of this experience is that he was making memories with his kids. However big or small, take the time to do the same.

Thursday Teaching {Lava Cups}

Project: Lava Cups

Concept: Floating Continued!

 Today's project is a continuation of Tuesday's lesson - why things float. (So be sure to check out Tuesday's foil boats for a more thorough explanation.) We'll use the same concept to create groovy retro lava cups. Mrs. V is not a big fan of written tests, but what she does love is when students can see a demonstration and explain what's going on. So I'm putting you on the spot of how to explain this project to your kids. I'll be gracious with some hints :) One of my professors of education said his high school students referred to him as 'the benevolent dictator'. I always liked that approach.

Materials needed: glass 3/4 full of water, 1/4 cup vegetable oil, 1 tsp salt, 5 drops of food coloring

It's debatable which is more fun - the actual experiment or the seriously cool food color art in the water!
Pour all the vegetable oil into your colored water. You'll notice that when settled, the oil floats to the top.
Why is this?

Is the vegetable oil more or less dense than water?

Slowly pour salt into the glass. The salt attaches to the oil, creating little pockets of oil and salt. So we've made the oil bubbles to be more dense now than the water. So they.... will...... now...... sink! Right, sink. Watch as the oil bubbles sink. Eventually, the salt will dissolve in the water, leaving the oil bubbles to be once again less dense than water. So they.... will....... now........  float! Again, float. Continue to add salt to achieve lava lamp-like effects.

Color number 2. I think the lighter color made the movement easier to see, although red is fitting for a 'lava' cup.

Oil + Salt > Water

See the movement?

*Special thanks to sciencebob.com for some inspiration behind today's project!

Tuesday Teaching {Foil Boats}

Project: Foil Boats

Concept: Displacement

Dictionary.com says: the weight or the volume of fluid displaced  by a floating or submerged body.

 I say for your kiddos: the amount of water that is pushed away by an object

What happens when you get into the bathtub? The water level rises a little. This is because you are taking up space where some of the water used to be. You're replacing the water. An object in water always pushes the water away and takes up that space. This is true for foil boats:

Ok, so we know the water gets pushed aside by an object. Well if all objects replace water, why is it that some objects float and some sink? Well, the simplest answer for your kids is this:

If the green space is heavier than the same amount of water it pushed aside, the object sinks. 

If the green space is lighter than the same amount of water it pushed aside, the object floats.

Think about the tinfoil. The green space of the boat is tinfoil and air, a much lighter combination than water. So the foil boat floats! But as we fill up the green space with more and more weight, the boat becomes heavier than the amount of water it replaced. So eventually, it will sink.

Experiment with different shapes of boats. Have your child brainstorm different kinds of boats they've seen. In my example, I'll show you just two: a sailboat and a raft.

Materials: 'lake', weights (I'm using pennies, but wouldn't it be fun if you had Pirate LEGO men!), foil.

Sailboat foil size (before making the boat): 9 inches x 5.5 inches

Raft foil size (before making the boat): 4.5 inches x 5.5 inches

Be creative with your design. Just make sure you don't have any tears in the foil and that the sides of the boat are at an even height.

How many pennies do you think these boats can hold? Ask your kids and get them thinking.

Let me know how you did! Send a picture and a count and I'll showcase our big winners.

Numbers to beat so far:

Mrs. V - 65 pennies in the sailboat

Mrs. V - 50 pennies in the raft

Holding strong!

And.. sunk.

Raft with pennies - Notice how they're distributed evenly? We want this boat balanced!

And... sunk.

The sunken ships recovered

Extension to this project:
Cardboard Boats. Life-size cardboard boats. This was the highlight of the year for the engineering students. Felix Slade's example here:

Cardboard Boat Race 2010

As always, let me know in the comments if I need to tweak my explanation. Also, I have been generous and loose with the terms here so your kids can make some sense of it. So teach these basics, but if your kids come up with some objects that disprove the theory or they start getting into something above your head, that is awesome!!! There are lots of other principles that affect displacement of an object, so write me a comment and I will teach, teach, teach some more!

Thursday Teaching {Balancing Bird}

Project: Balancing Bird

Concept: Center of Gravity

Wikipedia says: "The center of mass is often called the center of gravity because any uniform gravitational field g acts on a system as if the mass M of the system were concentrated at the center of mass R."

I say for your kiddos: It's 'the average location of the weight of the object'.

Explanation for the kids:

Take a ruler or a pencil. You can find the center of gravity of these objects by balancing them on your finger. I'm sure you did this in Mr. Wengel's English class trying to stay awake, but it's probably totally new to your kids!

Well, this is relatively easy because a ruler and a pencil more or less have a uniform shape all the way around. The bird we are about to do doesn't have a uniform shape, so we'll have to make some adjustments.

Finding the balance point of a paper bird is not impossible using a steady hand and a pen, but your kids will have more fun flying around the house with their bird on their finger.

You can see that the center of gravity is not very close to the beak. How could we move the center of gravity? Well, we need to make the beak the place where there is equal weight on both sides of the bird. So, we have lots of paper on the back half of the bird, but very little paper on the front half.  We need to add something more to the front half to make both sides even. We'll add some weights. Make sense?

Use paper that is thicker than computer paper: cardstock, construction paper, cardboard, etc. In general, the thicker the better!

Draw your bird. This is a general shape, but have fun with it. The only requirement is that the wings extend past the bird's head.

Cut and color and color some more. Bow inspired by the adorable little girl sitting next to me.

Add pennies on wingtips (with tape - Gluing is illegal :))  and balance! It may take a couple tries to get it just right.

Switch pennies to the inside for maximum coolness!

For the older kids: Experiment with other animals or shapes. I've seen parrots and monkeys, so no holding back. Remember you're looking for even weight distribution. Ask if they can find a way to disguise the pennies on the outside - turn them into eggs, for example. See if you could get two birds to balance off each other. The possibilities are endless!