Download Kinetic potential August 11

Science Bus Week 1
Paul and Praj
Summer 2005: Energy
Kinetic and Potential Energy
Materials Needed
Introduction
A tennis ball
One bocce ball, or something similarly heavy (cricket, baseball, billiards ball)
2-liter bottle to act as bowling pin
A couple heavy duty rubber bands
Some paper folded into “wads” to be shot by rubber bands
Station 1 (Conservation of energy)
Bocce ball, or something else heavy
Some heavy duty tape
Heavy duty string, maybe 20ft worth
Someway to make a pendulum out of the above materials, with as big a radius as possible
Station 2 (Rockets and Planes)
The Rocket Balloons with pump (these can be borrowed from the physics department, or
purchased fairly cheaply at www.rocketballoons.com)
Cheap rubber-band powered airplanes, purchasable from hobby shop in MountainView
Station 3 (Odds and Ends)
A basketball
A Tennis ball
A ping pong ball
Some thin strips of paper, taped into rings
A racquetball, cut in half and trimmed to be a “popper”
One or two eggs
Introduction
Since this is the first week of the quarter, we will start with a general introduction to the
topic, energy.
Demonstration
Here, we will do a simple demonstration involving energy. First, we will set something
up, then have the kids vote on which one they think will “win,” then do the
Discussion
Now that we've introduced the concept of “energy,” we can start talking about different
kinds of energy. We'll begin by asking the kids to name different types of energy, and
then right them on the board. After they name them, we'll ask how that type of energy
can be used to perform work.
Some types of energy:
kinetic energy
chemical energy (explosives, ATP, pocket hand warmers, gasoline, coal, oil, etc.)
solar energy (photovoltaics, photosynthesis)
potential energy (gravity, electromagnetic, springs)
nuclear energy (the sun, power plants)
steam power
mechanical energy
mass energy (E = mc^2 !!!)
Many of these types of energy will be covered in future lessons, but this week we will
focus on potential energy and kinetic energy.
Kinetic Energy
Kinetic energy is pretty simple, really it's just energy in the form of moving objects. We
ask a couple of simple questions. If I have two bullets, and I take one of them and shoot
it with a gun and take another one and throw it, which one has more kinetic energy?
Why? What we're trying to get at is that things moving with higher velocities have more
kinetic energy.
Kinetic Energy Demo
Which has more kinetic energy? Something big or something small? Something slow
or something fast? We will demonstrate this by doing some bowling. One of the tutors
will attempt to knock down a water bottle using either a tennis ball or a bocce ball and
rolling it either fast or slow. The idea is just to demonstrate that the more massive and
more quickly something is moving, the more kinetic energy it has.
Potential Energy (with simple demo)
Potential energy is energy that is stored or hidden. Our first example of potential energy
will be a spring (actually, a rubber band). We will pull back the rubber band and ask the
kids whether or not there is potential energy stored in the rubber band. If they say “yes,”
we will ask them to explain how we can release the energy. Obviously enough, we will
shoot a wad of paper across the room with the rubber band, showing how we exchanged
potential energy in the rubber band for the kinetic energy of the wad of paper. The idea
being that potential energy can be converted into kinetic energy. We will then
demonstrate that more potential energy makes more kinetic energy by pulling the rubber
band back further and further.
Now, we'll try to get the kids to name other types of potential energy. In theory, many
will be written on the board behind us so this should work pretty well. We definitely
want them to get gravitational potential energy. To demonstrate this, we'll use the tennis
ball, and drop it from various heights and talk about its velocity at the bottom. The idea
being, the higher you raise the ball, the more potential energy it gets which translates into
more kinetic energy at the bottom. Why is this? Conservation of energy. We'll
discuss this more at one of the stations.
At this point, we will break the kids up into 3 groups and send them off to the three
different stations.
Station 1: Conservation of energy
Bring the kids in a group and ask them: why is it that a rubber band stretched back more
will go farther. Connect back to the concept of PE. That is, stretching it back more
gives it more PE. Then ask what happens to the rubber band when it is released. Where
does the PE go? The concept we’re trying to get across is that the PE is converted to KE.
Perhaps repeat the rubber band experiment, as well as demonstrating that the higher you
hold a ball, the higher it will bounce, and that it can’t bounce back to higher than it’s
initial height.
Finally, set up a pendulum outside. The easiest thing may be to simply have a yo-yo,
and hang it from the roof of one of the walkways. Or you can construct one from some
rope and one of the bocce balls, a pool ball, and a handkerchief. Have children release
the pendulum from right in front of their face. They will see that the pendulum will not
come up and hit them, but stop right before reaching their face. The bocce ball would be
better b/c the danger factor would make it more fun. Have all the children try this
experiment.
Station 2: Rockets and Planes
This station is going to try to emphasize the idea of doing work to give an object energy.
So, first we'll ask the kids to talk about how we used energy to do work in the previous
demo (the velocity made the paper wad fly across the room, the tennis ball knocked down
the water bottle, etc.). Then ask the kids how we were able to give the objects energy, if
they've been to the “conservation” station, then they'll know that energy is conserved and
that we had to put the energy in the object somehow. Explain that we had to do work in
order to give the object energy, so that it could do work.
For this station, we'll be storing energy in some simple things (balloons and airplanes) by
doing work on them, and then they'll release that energy by doing work (flying).
The rocket balloons are pretty simple: pump them up, and let them fly. Ask the kids
where are you doing the work? How are they getting the energy? What are they using
the energy to do? Try pumping them up a different number of times (1 pump, 2 pump,
etc.) and see how high they go. These are pretty safe, so you can let well-behaved kids
give it a try.
The airplanes are powered by twisting the propeller, which twists the rubber band, which
lets them fly. These are pretty cheap (a couple of dollars each), so we should have a few
there and we can let the kids try them out. Pretty much the same as the balloons, we just
count how many twists and let them fly. Ask the kids how they could fly further?
Lighter planes? More rubber bands?
Station 3: Odds and Ends
This station just has a couple of simple demos that don't really explain anything, but are
kind of fun. First, is the classic “basketball, tennis ball, ping-pong ball” launcher. What
we'll do is give the kids the ping-pong balls and see how high they can throw/ bounce
them. Then we'll see if we can do better using the “launcher.” If you get the demo to
work right, ask the kids why. Just try to get them to figure out that the energy that the
basketball and tennis ball had were transferred to the ping-pong ball, thus giving it extra
velocity. You might want to try the demo first with just the bball and the tennis ball.
This is a little easier to control. Try using the rings of paper to keep the balls steady
during the drop.
The last little bit involves using a “popper.” This is just a racquetball cut in half, and
then trimmed a bit. If you turn it inside out and drop it, it will “pop” when it hits the
floor, causing it to fly into the air. We'll probably have two of these so the kids can try
them out.
Conclusion
We won't try to get the kids back in the classroom, but instead we'll finish off by
summarizing the previous points (different types of energy, potential versus kinetic,
conservation of energy) and then doing a final demo.
Basketball and Egg
This is the same as the basketball and tennis ball demo, but with an egg instead of a
tennis ball. Perform with extreme caution.