Tag Archives: forces

Science Week 9: Pressure

I’ve got that David Bowie and Queen song stuck in my head this week…  “Under pressure…  Pushing down on me…”

Okay, now that we had a musical segway, onto pressure.  We began, as we usually do, by copying the definition of pressure into our science journals.  Then, to demonstrate right on the notebook, we each picked a colored pencil and experimented with different pressures.  You can see Mushroom at it below.  We also just tried putting pressure on different things and talking about the things that put pressure on us.

Then, we headed outside to hammer in some nails.  First, we tried hammering them in upside down to show how a sharper point can be influenced by pressure.

When we came inside, I showed them this video from Youtube where a teacher demonstrates laying on a bed of nails and having a cement block broken over another bed of nails on his chest.  The kids were as fascinated and appalled as the students in the video.  We used it to talk about how the pressure was spread out.  BalletBoy and Mushroom have actually lain on a bed of nails before at the Maryland Science Center, where they have a machine that allows the nails to rise slowly to ensure that the pressure gets distributed evenly.

Our next series of experiments came mostly from this website.  I’ve used some of their experiments before for other topics.  We tried the experiment with the lemon diver, where you make a little slice of lemon dive down by changing the air pressure, however, we couldn’t get a balloon to fit over the lid of the jar properly.  Doing the marshmallow faces also fizzled out.  I’m pretty sure the seal on the jar was airtight.  However, I think I might have needed to buy the really nice marshmallows to make it work.  I think the cheap ones weren’t puffy (and therefore air-filled) enough.

However, we did a number of variations on this experiment where you keep things dry by using air pressure under the water.  Even though it was simple, the kids were enthralled that you could hold air under the water.  Also successful was when I gave each kid a little bowl and a piece of cardboard.  When you fill the cup with water, put the cardboard on it and make a snug seal, you can flip it over and remove your hand.  The pressure will keep the cardboard in place.

To finish off our experiments with water, we put some holes into a plastic bottle and watched how the greater pressure at the bottom pushes the water out farther.  This was a good jumping off point to talk about how the changing air pressure can make our ears pop and how if you dive to the bottom of a deep swimming pool you can really feel the pressure.

To finish us off, I let the kids all try out the air pressure gauge for the tires on the car.  One tire was a little low, so we stopped and filled it on the way to take our science pals home.  I love it when science and errands come together!

Science Week 6: More Forces and Motion

We dipped into forces and motion for a second week of experiments and readings.  This week, we hit the Bill Nye episode about momentum and read a couple of the nonfiction section’s lesser offerings on the subject, including the book Forces and Motion: Questions and Answers by Catherine A. Welch.  This is one of those books that only asks you really obvious questions with simple, straightforward answers.  I guess I’m glad we had extra books to flesh out our pile, but I wish more science books for younger readers would treat their readers with more respect.

But on to the fun stuff.  We began by reviewing Newton’s three laws in the simplest terms.  For their science journals this week, the kids drew an illustration about each law.  Here are BalletBoy’s below.  The first law shows an apple falling (until stopped by Newton’s head) and an apple staying still.  The second picture shows someone trying to lift a big pile of books versus a single book.  The third picture shows the card houses we made last week – in other words, two forces balanced against each other.

Then we did experiments to think about each law.  For the first law, we talked about inertia again and pulled a piece of paper from below a cup full of water.  In other words, more magic.  We did a lot of these tricks last week.  This time, we moved on after that one.  Taking that same cup of water, I put a layer of oil on top then put four drops of food coloring.  We took turns slowly spinning the cup on the table so you could see that the liquid resisted moving.  In other words, it had inertia.

Staying with the liquid theme, I showed the kids two eggs.  One would spin easily.  The other resisted spinning, but once you got it going, it was harder to stop.  The one that spun easily could be stopped with a tap, but the other one kept going even after you stopped it with a light tap.  The kids had various ideas about this.  We ended up weighing the eggs on the balance to show that the difference in their weights was negligible.  Finally, I let them crack open the eggs.  The easy spinner was hard-boiled.  The one that didn’t like to spin (and then didn’t want to stop) was a raw egg.  We talked about what made that one different.  Overall, I think this was one of the most successful experiments we’ve done so far.  The kids loved trying to figure out the mystery and had many great (if not correct) ideas about what made the eggs act so differently.

Next, we continued with liquids by exploring centrifugal forces.  The kids made little buckets out of paper cups and string.  Then, they made quite a mess in the kitchen.

For the second law, we watched another Eureka video then did exactly what they talked about in the video.  We threw a heavy ball and a light ball.  I think, at least at this level, Newton’s Second Law may be the most intuitive.  The kids all know that heavy things are hard to move.  After all, they’re tiny and the rest of the world is huge.

For the third law, we did a classic experiment with a balloon taped to a straw and threaded on a string.  I tied the string to the easel on one end of the living room and the abacus on the other.  Of course, when you let the inflated balloon go, the force pushes it across the room.  This one delighted the kids.

So did playing with a gyroscope at the end of our experiment time.  The gyroscope did what they do and spun on the table.  We also watched an excerpt from the show Beakman’s World about gyroscopes.  The kids like that show much more than I do.  I find Beakman a little…  annoying.  Somehow when Bill Nye is manic on screen, it’s endearing, but when Beakman is, it’s just grating.  But hey, whatever works, right?

Science Week 5: Forces and Motion

And we’re back with forces and motion for science this week!  There are so many different ways to approach this topic.  We began, as we always do, with a pile of books.  The highlight was, as always, the Let’s Read and Find Out title, Forces Make Things Move by Kimberly Bradley.

However, we had another excellent title with the DK title Can You Feel the Force? by Richard Hammond.  That one began with a joke about THE force from Star Wars which really made the kids smile.  Ah, it’s the simple things that hook them, isn’t it?

After all that, I decided to focus on a couple of things.  We introduced Isaac Newton and his three laws.  Then we looked at the concepts of equilibrium and inertia (aka, the first law).  We’ll probably keep exploring those ideas in the next week or two, as well as adding new concepts.

The kids began by looking for ways to use force around the house.  I had each kid find a push and a pull they could demonstrate to the rest of us.  In the saga of how I’m continuing to figure out great ways to use our science journals, I snapped a quick picture of the kids demonstrating their pushes and pulls then printed them and taped them in the journals where they labeled them.  It worked very well.  Below is Mushroom showing us a push with the wheelbarrow.

And there he is pulling the string for the blinds.

Next we tried an experiment from the book Science Experiments with Forces by Sally Nankivell-Ashton.  We put things of various weights into a small box with a rubber band attached to measure how far the rubber band had to pull.  The measurement aspect was fun and it was nice to have a table to put into our science journals.

To introduce Newton’s laws, we turned to a video.  This was a very video intensive week.  Some of our videos are embedded below, so I hope you can click and enjoy the miracles of Youtube.  Here’s the first one, a Lego Sir Isaac Newton.  I can only hope my kids’ legomation gets as awesome as this kid’s.

And in case you just need a Bill Nye fix, here’s the parody song from the episode we watched.

To think about some of the concepts in Newton’s laws, we first started to explore equilibrium.  We used the balance that usually gets used for math to show off the idea of forces being equal.  Then we built card towers.  Next we had an excellent tug-of-war in the basement.  The kids tried some arm wrestling at the table.

Finally, we repeated the experiment BalletBoy got to demonstrate at the science show at Discovery Theater a couple weeks ago by hovering a ping pong ball with a hairdryer.  The kids loved it.  There’s BalletBoy showing them how it’s done.

Next, we began thinking about inertia by watching yet another short video, this time from the old Canadian show Eureka.  If you’ve never seen this show, it’s dated, but very cool and all available online in multiple locations.  This show has an odd feature in that it spends a full minute and a half talking about the other episodes, which is sort of off-putting for a 4 minute short.  Start your viewing at about 1:25 to see the actual show.

To demonstrate inertia, we did the trick where you pull a card from under a coin and a cloth from under a bottle.  The kids loved practicing it.  Then (and no one freak out) when we next got in the car, I demonstrated inertia by starting and stopping more abruptly than usual in the empty alleyway to let the kids feel their bodies go back and forth.  Two of the passengers thought this was great fun.  The other two clearly perceived that I was going to get them killed if I drove that way on the actual road and warned me never to do it again.  Such responsible youngsters.