Today in the 1-2 grade room we had a blast with some of the ideas we
need to use in making the water feature.
First, balance. I brought in two-meter-long sticks on pivots, along
with sets of weights of various sizes, and had the kids hang weights
in different places and then see where they had to place other weights
to balance it out. They quickly discovered that a small weight can
balance a large one, IF it is placed at the end of a long arm. This
was a really good exercise because, in contrast to some of our
previous ones, I had enough equipment for each child to explore
completely on his/her own.
The pre-snack period culminated with two capstone events:
(1) I gave the kids a worksheet in which I drew balance beams
with a weight on one side (varying the size and position of the
weight), and they had to draw the weight (size and position) they
would put on the other side. Mostly they got it right, and in the few
cases where there was confusion we had the equipment right there to
check if their drawing represented reality. (2) I demonstrated how
balance facilitates rotation. You can see a video I made about this
demo at the end of this blog post from last year. As kids went to break,
some of them commented how this demo is like the Moon going around the
Earth, and asking whether the Earth wobbles a little as it does so.
The answer is yes, and so does the Sun as the planets (Jupiter has the
biggest effect) go around it. Therefore, if you saw a star which was
wobbling, what could you conclude about it? Right, it has planets!
This is really how astronomers do it; the vast majority of planets are
too faint to see directly given the glare of their host stars.
Post-snack, we switched to fluid mechanics. We started by reviewing
what we learned about pressure last time, focusing on why water
doesn't fall from a straw when you cover the top with your finger. I
then showed the same idea in slightly different form: with two 2-liter
soda bottles screwed together, water does NOT fall from the top one to
the bottom one (it may drip, but it doesn't make the waterfall you
might expect in an open-bottle situation). The water doesn't fall
because for the water to go down, the air in the bottom bottle has to
move up, and the two get in each other's way. We then figured out how
to make them not get in each other's way: swirl it to make a "tornado
in a bottle." The air goes up through the middle while the water
swirls down around the outside.
We then took some time for each kid to make his/her own tornado in a
bottle, with the option of coloring and/or glittering the water. This
was great fun; the kids were really into it and came up with some
pretty (and/or Halloweeny) combinations.
Next, we studied floating and sinking, following more or less the
script from one of my Primaria sessions last year (adding a bit of
sophistication such as introducing the word density). But we had time
only to get to the egg in the salt water. We'll do the rest next time.
At the last minute, we stumbled into a nice connection between the egg
and geology. Teacher Pa said that the way to tell if an egg has gone
bad is to see if it floats (in non-salted water). Linus had said just
5-10 minutes before that pumice is a rock that floats because it has
lots of gas bubbles in it. So the connection is that an egg which
floats (without the help of salt) probably has gas bubbles in it,
which clearly is a sign that it's going bad.
Friday, October 26, 2012
Friday, October 19, 2012
Hydrodynamics 101
Today I worked with the 1-2 graders to extend their concepts of force
and motion to include work and energy, and then, after the break,
fluid dynamics.
While waiting for the kids to come back from chorus to start science,
I sat with one child who hates chorus, and we interleaved the pages of
two phone books. When science started, we talked about friction and I
used the phone books as a demo. The friction of 200 pages trying to
slide past 200 other pages is so much that two strong adults cannot
bull the books apart. Mythbusters had a great episode on this, in
which they used bigger (800 page?) phone books and couldn't pull them
apart even with cars. They finally resorted to military tanks, and
found that it took a force of 8,000 pounds to separate the books!
We then talked about work, which is applying a force over some
distance. Sitting in your chair, you are applying a force (your
weight) to the seat of the chair, but you are not doing work.
Exerting a large force (eg lifting a heavy weight) over a large
distance makes for a lot of work. We related this to irrigation
because the kids are studying the community, and are about to learn
that farming really took off around here when large pumps became
available to move the water.
Energy is the ability to do work, and we spent a looong time talking
about different forms of (mostly stored) energy: food, chemicals,
light, heat, electricity, etc. We spent a loooong time figuring out
what makes the electricity that comes to our houses!
Then came break. After break we finished up a few more forms of
storing energy: magnets, rubber bands, springs, etc. But mostly we
moved on to discussing how water moves (fluid dynamics). I did the
"three-hole can" demo (see paragraphs 3-4 of this post) to introduce
pressure and the relationship between pressure and water height. Then
I did the finger-on-the-straw demo (paragraph 6 of that post) to show
that the air also exerts pressure. Next was a siphon tank demo, to
show that air pressure can sometimes help quite a bit in moving water.
This demo did not work well, possibly because of a leak, so see this
video. Finally, I did the balloon in a bottle demo (paragraphs 6-8 of
the post linked to above) which is very analogous to the
finger-on-the-straw demo but far more dramatic....I could see Teacher
Ethan do a double-take when he first saw it.
Then I led the kids through designing different water systems on the
whiteboard. I supplied basic ideas such as water flowing into a
shovel on a pivot, and asked them to predict what would happen (when
the shovel fills with water, that end pivots down, dumping the water
out). We went through a bunch of these ideas, and I made sure to lead
them to realize the need for a pump to cycle the water back from the
bottom to the top. By this point they were very eager to start
drawing their own ideas, which played right into my plan. We had a
great time making posters of our ideas. In the last five minutes, I
unveiled the hydrodynamics kit which they will use in free-choice time
(or whenever Teacher Pa deems fit) to actually implement their ideas.
Overall, I think it went really well. We discussed a lot of ideas,
without overwhelming the kids, and the poster-drawing session was both
fun and educational.
and motion to include work and energy, and then, after the break,
fluid dynamics.
While waiting for the kids to come back from chorus to start science,
I sat with one child who hates chorus, and we interleaved the pages of
two phone books. When science started, we talked about friction and I
used the phone books as a demo. The friction of 200 pages trying to
slide past 200 other pages is so much that two strong adults cannot
bull the books apart. Mythbusters had a great episode on this, in
which they used bigger (800 page?) phone books and couldn't pull them
apart even with cars. They finally resorted to military tanks, and
found that it took a force of 8,000 pounds to separate the books!
We then talked about work, which is applying a force over some
distance. Sitting in your chair, you are applying a force (your
weight) to the seat of the chair, but you are not doing work.
Exerting a large force (eg lifting a heavy weight) over a large
distance makes for a lot of work. We related this to irrigation
because the kids are studying the community, and are about to learn
that farming really took off around here when large pumps became
available to move the water.
Energy is the ability to do work, and we spent a looong time talking
about different forms of (mostly stored) energy: food, chemicals,
light, heat, electricity, etc. We spent a loooong time figuring out
what makes the electricity that comes to our houses!
Then came break. After break we finished up a few more forms of
storing energy: magnets, rubber bands, springs, etc. But mostly we
moved on to discussing how water moves (fluid dynamics). I did the
"three-hole can" demo (see paragraphs 3-4 of this post) to introduce
pressure and the relationship between pressure and water height. Then
I did the finger-on-the-straw demo (paragraph 6 of that post) to show
that the air also exerts pressure. Next was a siphon tank demo, to
show that air pressure can sometimes help quite a bit in moving water.
This demo did not work well, possibly because of a leak, so see this
video. Finally, I did the balloon in a bottle demo (paragraphs 6-8 of
the post linked to above) which is very analogous to the
finger-on-the-straw demo but far more dramatic....I could see Teacher
Ethan do a double-take when he first saw it.
Then I led the kids through designing different water systems on the
whiteboard. I supplied basic ideas such as water flowing into a
shovel on a pivot, and asked them to predict what would happen (when
the shovel fills with water, that end pivots down, dumping the water
out). We went through a bunch of these ideas, and I made sure to lead
them to realize the need for a pump to cycle the water back from the
bottom to the top. By this point they were very eager to start
drawing their own ideas, which played right into my plan. We had a
great time making posters of our ideas. In the last five minutes, I
unveiled the hydrodynamics kit which they will use in free-choice time
(or whenever Teacher Pa deems fit) to actually implement their ideas.
Overall, I think it went really well. We discussed a lot of ideas,
without overwhelming the kids, and the poster-drawing session was both
fun and educational.
Monday, October 15, 2012
Understanding the gravity of the situation
Last Friday with the 1-2 graders we reviewed and extended our
observations of force and motion which we began two Fridays ago,
before the Yosemite trip. Because it had been two weeks, we started
with quite a bit of review, which I did by asking the kids questions
rather than lecturing to them. We observed the motion of a rolling
ball in order to change the context from last time (when we used a
hoverpuck or a marble shot out of a blowgun).
I had them observe and draw some motions. This addressed California
Grade Two science standards 1a and 1b, as well as built the case for
the following argument.
By observing a ball thrown up in the air, we concluded that there is a
force on it even when I am not touching it, and that that force is
simply gravity. I then repeated the donutapult demo to refresh their
thinking on how something goes in a circle only when there is a force
on it; if there is no force on it, it will go off in a straight line.
Then we talked about the Moon and how there must be a force on it
because it goes in a circle around the Earth. That force is also
gravity!
(I think the following was too advanced, but we did discuss it.
Gravity always points to the center of the Earth. One student is
going back to Korea soon, so I drew Davis and Korea on a globe and
showed how this must be the case. Then I noted how the force on the
donut also points to the center of its "orbit" because that is the
only direction the string can pull. So there is very strong reason to
think that the force on the Moon is Earth's gravity, the same force we
know and love, that makes things fall when we drop them! [Standard 1e])
After the break we discussed how to send forces in different
directions and in different amounts by using simple machines such as
levers, pulleys, and gears. I had brought in the Gears!Gears!Gears!
toys earlier in the week, so they easily got the basic idea of this
standard (1d). But I lost them when I got into the details of
levers...they weren't able to predict where to place a lever and a
fulcrum to perform a given task, nor were they able to draw arrows
indicating the sizes of the forces at the different ends of the lever.
And I didn't really have the equipment handy to do real hands-on work
with that, so I may do this again this Friday with better equipment.
observations of force and motion which we began two Fridays ago,
before the Yosemite trip. Because it had been two weeks, we started
with quite a bit of review, which I did by asking the kids questions
rather than lecturing to them. We observed the motion of a rolling
ball in order to change the context from last time (when we used a
hoverpuck or a marble shot out of a blowgun).
I had them observe and draw some motions. This addressed California
Grade Two science standards 1a and 1b, as well as built the case for
the following argument.
By observing a ball thrown up in the air, we concluded that there is a
force on it even when I am not touching it, and that that force is
simply gravity. I then repeated the donutapult demo to refresh their
thinking on how something goes in a circle only when there is a force
on it; if there is no force on it, it will go off in a straight line.
Then we talked about the Moon and how there must be a force on it
because it goes in a circle around the Earth. That force is also
gravity!
(I think the following was too advanced, but we did discuss it.
Gravity always points to the center of the Earth. One student is
going back to Korea soon, so I drew Davis and Korea on a globe and
showed how this must be the case. Then I noted how the force on the
donut also points to the center of its "orbit" because that is the
only direction the string can pull. So there is very strong reason to
think that the force on the Moon is Earth's gravity, the same force we
know and love, that makes things fall when we drop them! [Standard 1e])
After the break we discussed how to send forces in different
directions and in different amounts by using simple machines such as
levers, pulleys, and gears. I had brought in the Gears!Gears!Gears!
toys earlier in the week, so they easily got the basic idea of this
standard (1d). But I lost them when I got into the details of
levers...they weren't able to predict where to place a lever and a
fulcrum to perform a given task, nor were they able to draw arrows
indicating the sizes of the forces at the different ends of the lever.
And I didn't really have the equipment handy to do real hands-on work
with that, so I may do this again this Friday with better equipment.
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