(Mostly) Wordless Wednesday: The Big Launch

This was the big finale of our Astronomy/Rocket science class, launching at NASA Goddard!

Out of 16 kids, I believe everyone had at least one successful launch, and most had two launches.  Super fun on a beautiful day!

Seven Quick Takes: Great Book Combos, Cake Fails, and Shark Teeth

 1.  My friend Bill pointed out that you rarely see The Agony and the Ecstasy and Electronics for the Evil Genius on the same shelf.  I suppose he's right. 

I feel like there's something about this book shelf that encapsulates my life.

Big Enough

2 .  I am always on the look out for spots with poor drainage so that when we get a few days of rain we can have a Ducky Day.

This involves putting on rubber boots and hunting down the biggest puddle we can find... After a thorough soaking, we head home for baths, popcorn and hot chocolate!

We started this when Mxyl and Klenda were toddlers, but if you get a big enough puddle, everyone still wants to play!


3. Joy!  Rapturous delight!  This year I used my birthday money to buy a tree peony!  This is a long term investment, but, over the next 50 or so years this graceful plant will get about 6 feet high and 8 feet wide with progressively larger flowers.

This year I get three blossoms this size (8 inches of petals that look like they are cut from iridescent purple silk).

 4. Have you ever made something you were sure was going to be wonderful, and right about the time you are finishing, you suddenly realize...

That it's a terrifyingly creepy dinosaur cake that looks like it's planning to eat your head?

Yeah.  I know. We all go through that.

Fortunately the cake was for Choclo, and he declared it his favorite cake ever.

Trekking to the beach at Purse Park

 5.  It's shark tooth season!  We live in Maryland, in a spot that was covered with a shark infested sea (30 million years ago).  Yes, some people probably would try not to think about that too much.  But we find this wonderful: since each shark has thousands of teeth throughout it's life, our soil is embedded with millions of fossil teeth!

From Bayfront Beach

Fortunately, we don't have to dig for them.  They are continually washed out of the soil and found on the banks of rivers and the Chesapeake Bay.

Which means, on pleasant spring days, we spend the day at the beach,  playing in the sand and enjoying the water collecting fossils.

These are teeth, ray plates, and bone fragments (from whales and dolphins) from our latest day off scientific expedition.

If you're wondering why this is seasonal, I have two words for you: jelly and fish.

6. We finished our model rockets this week! We will meet one more time on Sunday to launch at NASA Goddard (I really do love saying that!) and we are done with our Astronomy and Rocket classes.  Hooray!  So fun!


7. If you are wondering what happened to The Big Trip, we are still traveling in Japan, although we will be leaving soon for Mongolia.  Blog posts coming soon, I promise.  We just got snowed under with birthdays, anniversaries, and end of year craziness.

If you are wondering what the heck that's about, the short answer is that we came across a truly enormous pile of imaginary money, and we have been using it to take a once in a life time trip around the world.  You're free to join us, and/or if you live someplace we will, or should be going, to have us "stay" with you!

Happy weekend!  More fun with Jen!

Kids' Rocket Science: Third Law of Motion

 The third law is the one everyone remembers: for every action there is an equal and opposite reaction.

The favorite demonstration of this is the Newton's Cradle.  Perfectly equal and opposite reactions!


Having done this lesson a number of times, here is my advice: yes, you need a Newton's Cradle; no, you can't make one yourself; yes, you will need a new one each time because the kids will play with it until they tangle the lines irretrievably.  The good news is that it's less than $10 counting shipping. Do not take it out of the box until just before class time.

An interesting  part of the equal and opposite law is what I think of as the "billiards corollary" because this is how professional pool sharks actually make their shots.  When a ball strikes another object, it bounces off with equal force (minus whatever was absorbed by the object) in the exact opposite direction (at the opposite angle).  Lacking a pool table, we showed  this by rolling golf balls against the wall at different angles.

It's easy to see how this law works when things are moving, but most every day encounters with it are fairly static: when you sit down on a chair, you are pushing down on the chair with your entire weight, say, 100 lbs. The chair is pushing back 100 pounds. One kid asked what happened if the chair didn't push back, the answer is that if the chair can't push back enough, it breaks and I fall on the floor, which hopefully can still push back enough!

My favorite way of looking at this law is by having two kids (of roughly equal mass) stand on skateboards and push each other.  Lacking skateboards, I had them take turns standing in our wagon and pushing against me. Of course, as hard as they pushed, they moved away!

That led to a conversation about recoil: cannons, guns, baseball bats, and so forth.

 Then it was time to make the Alka-Seltzer rockets.  When I was setting up the class, I ran a few test flights to make sure that my Alka-Seltzer tablets were still good.

The good news was that the tablets were fine.



The bad news was that some of my old film canisters (which I had successfully used for this the last four times I ran this class) were no longer holding pressure. 

 Worse news: during the actual class, all the canisters, even the ones that had worked for the tests failed.  The farthest a rocket got was 6 inches off the ground! Usually we can get 20 feet in the air!

What a disappointment.

 

So I decided to do some tea rockets instead! 


Not a perfect demonstration of the third law, but much more satisfying!


 And I could use the left over tea to serve the class tea and strawberries!

Kids' Rocket Science: Second Law of Motion

 The Second Law is probably the hardest to explain to young kids: F=ma.  Force is equal to mass times acceleration.  I like to put it as: "The heavier it is, the harder it is to push.", and "The harder you push the farther it goes."

The fact is, it's more specific than that.  If push something exactly twice as hard, it goes exactly twice as far.  If something is exactly half the mass of the first thing, it will go exactly twice as far, all other things being equal.

 We looked at this several ways.  I used a very light ball, and a sand filled ball that happened to be a similar size, and tried tossing them. This is good because it confirms their everyday understanding that, yeah, you have to use more force to throw a heavier ball. Naturally, any boys in the class will try to throw the heavy ball as far as possible, but, in my view, that's okay- they can feel the extra effort it takes to heave the extra mass.

Then we tried dropping the two balls in the sand box.  This was actually a better experiment because you could easily see the dents left behind by the two balls (the heavier ball left a deeper dent because it fell with more force, while the acceleration of gravity was constant)

We also rolled real golf balls and foam golf balls (you could use ping pong balls) down an incline and saw that the more massive balls rolled farther. Again, this is somewhat more useful than throwing because the gravitational acceleration is constant when you use gravity.

It also explains why, in the Pinewood Derby, you are not allowed to have your car weigh more (have more mass) than a certain standard.  It would be an unfair advantage because the heavier cars would always win.

Now, I did say these rules applied with all other things being equal... Such circumstances are pretty rare on Earth.  A baseball hit with twice as much force won't actually go twice as far.  Why not?  One reason is that it will have gravity pulling on it for a longer  time since it will be in the air a longer time. Another reason is that it has to travel through more air, and therefore more air resistance.

Ah, air resistance.  That's pretty important when you're talking about rockets.  How far can you throw a piece of paper?

Try throwing a plain flat sheet of paper as hard as you can.  It's pretty hilarious, actually.  One of the kids immediately suggested that we wad it up into a ball.  That went much farther, even though it was the same mass as the flat sheet.  Then I folded a sheet into a paper airplane, and that went clear across the room and pegged Zorg.  Sorry, Zorg!

 We made Puff Rockets from this printable pattern.  They are designed to have a very low mass, as well as minimal air resistance, and they go remarkably far on a puff of air (provided by you!).

You can also experiment with flying them with and without the fin assembly.  It really lets the kids discover for themselves why rockets have fins.

 Super fun!  Thank you Mxyl for the pictures!

Kid's Rocket Science: First Law of Motion

 Shifting gears from Astronomy to Physics, today's class was about Newton's First Law of Motion: a body at rest tends to stay at rest, a body in motion tends to stay in motion, unless acted upon by an outside force.

We started out defining force as a push or a pull on something (although there are forces like drag that are a little less straight forward than "push/pull").

And we defined mass again: it's how much "stuff" is in you (as opposed to volume: the amount of space you take up). So, you can see that the scale measures a force (gravity pulling down on a certain amount of mass), while the balance measures mass (this much mass over here is equal to that much mass over there).

The first half of the law is easy to demonstrate: a body at rest (a lab assistant) tends to stay at rest, unless acted upon by an outside force (alarm clock).   I also set up a model rocket and let the kids do a countdown to... nothing happening.  Without the engine to provide an outside force, it just sits there!

But there are more fun ways to show this: we gave each kid a cup, a card (to set on the cup) and a quarter (to set on the card).

When you flicked the card away, the quarter tended to stay in place until acted upon by an outside force (gravity), at which point it fell into the cup.

We also did the quarter on the elbow trick. And I used a string of rubber bands to drag a large (smooth bottomed) rock.  You can measure the force it takes to move the rock by the length of the bands.  The bands stretch a long way to get the rock moving, but then they shorten up as it continues moving.

The fancy term for the first half of Newton's First Law is inertia, while the fancy term for the second half is momentum.  Once you start looking, there are practical examples of both everywhere!

Think about how difficult starting a hula hoop versus keeping it going or balancing a still bicycle, versus a fast moving bicycle.

Let alone biking up a big hill from a standing start!

Perhaps most importantly, these laws tell you exactly why you should wear seat belts.  To demonstrate this, we played a game I'll call Train Wreck.

I had a ll the kids form a train behind me, an off we went.

After we picked up some speed, I stopped quickly.  Train wreck!

There are some other fun ways to use momentum.

 For example, eggs.  Of these 18 eggs, 6 are hard boiled.  I had the kids spin them to determine which ones were raw( how's that for bravery in the name of science?!).

If you spin a raw egg, stop it briefly (with a light touch), and let go, the liquid inside will continue to spin,and the egg will turn.

You want us to what?

A hard boiled egg will take a tiny bit more energy to stop, but it will stay stopped.

 And, of course, there's always spinning around until you get really dizzy.  That's the momentum in the fluid of your semi circular canals, incidentally.

So that's about it.  Am I missing something?

Oh, yes, the rockets!!

This week's rocket is the balloon rocket.

We ran strings between chairs for a track (2 tracks per set of chairs so they could "race.").

We clipped a section of drinking straw  and put it on the string to attach the balloons to the strings.

We blew up the balloons (without tying them off) and gave it a go!  And it totally did not work.

I had only been able to find round balloons instead of long tubulat balloons.  The round balloons can't be oriented enough along the track to make this experiment work as planned.

So they took the balloons outside and raced them in crazy patterns on the lawn, so, no harm done!

My young cousin got the brilliant idea to put a penny in the balloon.  It takes a bit of shaking, but once the penny gets going, it spins along the interior of the balloon for a long time: inertia and momentum!!

At the end, we had a bit of extra time, so we threw Oob a little early birthday party, much to everyone's satisfaction.  Balloons and cupcakes, what's not to like?

Kids' Astronomy and Rocket Science: the Big Picture

 Okay, technically, it's not rocket science.  It's model rocket science.

And it's super fun!

We started our younger kids science class last Thursday.  I have 11 students aged 6 to 12 (including Oob, Choclo, and Leena) and 5 older lab assistants (including Zorg, Klenda and Mxyl, our staff photographer).  All photos will be from from Mxyl.




Here's how our class is set up:
1 Motion and Distance
2 Earth and Other Planets
3 The Moon
4 The Sun and Other Stars
(Easter Break)
5 Rockets: Newton's First Law
6 Rockets: Newton's Second Law
7 Rockets: Newton's Third Law
8 Visit Observatory (at night!)
9 Build Rockets
9.5 Optional extra build class for older kids and fancy paint jobs
10 Launch Rockets at NASA Goddard

I'm drawing a lot from Janice Van Cleave's Astronomy for Every Kid, and from the rocket program developed by my cousin, Ed (whose granddaughter is taking the class!).   I'll post all the materials and sources as I go - most of it's free, either printable on line or stuff you probably have.  The exception is the model rockets themselves.  I'm getting them in a class pack from AC Supply - way the cheapest and easiest way to do it.

Cheapest because it breaks down to $15-$20 a complete rocket (including 2 engines per rocket) counting the shipping.

 Easiest because I'm getting rockets with pre-molded fin assemblies.  If you are doing this with single digit kids, this is the way to go.  Older kids can get their own fins on straight, but with younger kids, it's an exercise in frustration..

I've now done the rocket program three or four times and I keep adding on and fiddling with it.  I blogged about the rockets last time in 2011.  This time around, each class is an hour.

Rockets!

 We've finally finished our laws of motion rockets and built "real" model rockets to launch at NASA Goddard!

Here they are on the launch pad from left to right: Choclo's, Mxyl's, Klenda's, Oob's, Zorg's, and Leena's.

We had used a bulk kit of 12 Astra IIIs, and, yes, we made all of them (although some were for other kids in the class).  Our family did seven of them because Choclo made one for the Emperor as a birthday present.

 I chose this kit because it had a pre-molded fin assembly - much easier than working with balsa wood, exact-o knives, and small children!

It was quite easy to build, and the fins were beautifully straight.  In fact, the rockets really came out beautifully, except....

The pre-molded launch lugs were too small for the rails.  In the top picture, you can see that each rocket is strung on to a metal rod or "rail."  This is important because the rails guide the rocket straight up .  Every model rocket has a "launch lug" which is the part of the rocket that rail goes through. 

What you are actually seeing in this picture is the pros (the one in the hat is the launch officer and our first cousin, once removed) trying to get the launch lugs to stretch out enough so that the rockets will move smoothly on the rails.

After all the building, it is incredibly frustrating to have the rocket not work correctly because of a problem  that came from the factory!

They actually worked our rockets enough that they were able to launch, but, of the other kids in the class, only one was able to launch.

Still, it's an ill wind that blows no good.  The friction on the rails reduced the altitude of the rockets, but then, since they didn't go as far, we had a much better recovery rate.  We retrieved 6 of the 7, and we usually only get half of them back....

We plan to enlarge the holes on the launch lugs and try again next month!

Rocketing Along

 We did the second law of motion today: F=ma!  This means, Force equals motion times acceleration.  Which means if something is twice as heavy, you have to push twice as hard.  To which you respond, I knew that.

It also means that if it's not twice as heavy and you push twice as hard, it'll go twice as far (not counting pesky things like friction and such).  Which I'm sure you also knew, but doesn't it look nice dressed up as F=ma?

This is a fun one to demonstrate, but first, (IMHO) it's important for kids to learn the difference between mass and weight. I tell them that mass is how much stuff you have inside you, and weight is the downward pull (from gravity on your mass).  Then I show them the difference between a scale and a balance.

I brought out 4 scales: an old one which shows the most clearly that it's the push that moves the needle, an old postal scale, an old dial stand on scale, and a new digital scale. I think the kids could have spent the entire half hour weighing themselves and random objects.

Then I built a simple balance (as in triangular block topped by a bar of wood simple) and showed them how that worked.  Weight doesn't have much to do with it, really, you are balancing equal masses (in my case rolls of tape).  My simple balance would work on Neptune, or the moon, or even the sun (OK, maybe it would burn up on the sun, but in principle it would work!).  None of the scales are any good except on Earth!

Next we lifted weights so they could feel twice as heavy means twice the work.  It was a little difficult to get the boys to admit that twice as heavy was twice as hard...  Usually I use a medicine ball and a playground ball for this (which would have been better, I think), but I couldn't find the medicine ball. :(

Then we rolled toy cars off a ramp, adding pennies to increase their mass.  Sure enough, the more mass, the farther it went!  Here is where things started to go wrong, however.  I hadn't thought of the issue that I was using Choclo's cars.  He took great umbrage (and most of the cars) before he was done and I had to banish him to his room.

Alas, that did not put him in a good frame of mind to start cutting and taping the Puff Rockets (printable pattern and instructions here).

I had hoped that the older Zoomlians had done this recently enough to help out the younger kids.  It was not so.  If I had it to do over, I would have done it with the older kids the day before so they could really assist.  As it was, everyone was lost in the sauce and wanted HELP! RIGHT NOW!  while I needed to help the two youngest kids whose mom would be arriving real-soon-now to take them home.

At this point, Choclo and Oob began chasing each other at top speed in laps around the house (through the room we were working in) while shrieking loudly.  Yes, we do have days like this.  Not many, but some!

We did get everyone's rocket done, and everyone loved them, and went outside to play loudly with them there, so I guess all's well that ends well!

But now I need a nap.

Return to Science

We started up our Science class this week.  This semester we are doing Physics, and we are starting with rockets.

Specifically we started with Newton's first law of motion: "Something at rest stays at rest, and something moving stays moving unless acted on by an outside force."

We started off with the inertia side.

Did you know that if you drop your clothes on the floor, and no one picks them up, they will stay there for hundreds of years?  It may be propaganda, but it's true!

We went on to do the jar and coin trick - you place a quarter on an index card over a jar, and then flick the card away.  The coin's inertia causes it to remain stationary, then gravity drops it into the jar.  They ended up able to do it with a stack of coins.

I had Mxyl and Klenda show them the catching the coins on your elbows trick.

Than I slowed it down a bit and showed them inertia by pulling a heavy coffee can with a rubber band.  This is nice because the rubber band shows (by it's length) how much force you are using.  You see the band lengthen until the can starts moving, and then contract as it uses less force to keep moving.

Next we went to work on the momentum side.

First we talked about riding a bike: how hard it is to do a standing start uphill, and how hard it is to balance on a still bicycle.

Then we practiced with a hula hoop - this actually shows inertia (you give it a hard push to start it) and momentum (once it gets going it's a lot easier to keep it going).

We moved on to our dump truck demonstration.  I couldn't find enough little people, so we added a pony for pizazz.  On the plus side, one of the little people was missing the top of his head so I could show them, Look!  He has no brains, he thinks it's a great idea to ride in the back of a dump truck!

Off they went, straight into a wall, and even the youngest kids got it - that's why we wear seat belts! 

Everyone felt the need to repeat that demonstration, so I was able to set up the balloon rocket experiment. 

The balloons were a real hit, so we eventually took them off the tracks and just zoomed them around the room!