Don't Lose Your Marbles Over Potential and Kinetic Energy

There is a great teachengineering.com activity that reinforces the learning about potential and kinetic engineering.  In it, the students use a 6 foot section of pipe insulation cut in half to build roller coasters.  It is a great way to get them to begin to understand how mass, gravity, force, Newton's Laws and Potential and Kinetic energy work on a physical level.

Educational research shows that if you read about a topic you retain about 10%, if you only listen to a lecture about a topic you retain about 25%, 30% retention if you see the topic demonstrated, if you see and hear you retain about 50%, and if you see, hear, and repeat you retain about 70%.  However, if you see, hear, repeat or say something about the topic and use the ideas, you will retain about 90% of the ideas.  I am hoping that all the 4th graders at this school will now remember potential and kinetic energy.

In this activity, the students build roller coasters and use a marble to run down the track and try to get the marble in a cup.  They get various points for different design characteristics, which include: 90 degree turn, 180 degree turn, 270 degree turn, a loop, and a corkscrew.  The students quickly learn that the corkscrew is the most challenging, followed by a large loop.  Small loops are easy and can be combined with other attributes such as a 180 degree turn.  As an added challenge, they had to use different marbles with different masses, a glass marble weighing 3.5 grams and a steel marble weighing 7.5 grams.

Here are just a few of the designs they produced.

A loop d' loop.

Corkscrew with a loop

Loop with 180 degree turn

Another double loop

Fun with Roller Coasters

We had planned to have a fun science/engineering day back in December just before winter break with the 3rd graders.  But a bug struck our family and had us down and out for the two weeks before break, so I had to cancel this session.  I spoke with the teachers and we decided to go ahead and use this one out of sequence for our session this week.  What a great time the kids had!  They all proclaimed that this was their favorite activity we have ever done (which is saying a lot since I have been doing science with these kids since kindergarten!).  I used a writeup from teachengineering.org called Building Roller Coasters.  The grade level rating on this exercise is grade 7, but the third graders did great with this activity.  I have also seen something similar written up in Exploratopia (pg. 155).  Both activities use pipe insulation cut in half.  Each team of three was given a cup with a glass and a steel marble, a 6 foot piece of pipe insulation, 12 inches of masking tape, a pencil, and a scoring table.

Roller Coaster Scoring

Roller Coaster Features	Points	Your Design
Height	1 point / 12 inches
90 degree turn	1
180 degree turn	2
270 degree turn	3
Loop	3
Corkscrew	4
Each marble in cup	3
TOTAL POINTS

We talked a bit about potential and kinetic energy, asking the students if they could explain what each meant, and we also talked about acceleration and deceleration.  We then let them go build.  The most points awarded was for a corkscrew, which is the most challenging to build with the six feet of pipe.  Here are a couple of examples of corkscrew designs that worked.

The most popular design by far was the loop.  It also resulted in some good learning, too.  One group in particular was struggling with their loop.  The marble was making it about 2/3 of the way up the loop and falling out.  They couldn't figure out what was wrong.  I sat with the group and started asking them questions:

Why is the marble falling out?

          Ans:  It is not going fast enough

How can you help it get up the loop?

         There was a bit of discussion among the group, I hinted that there were a couple of solutions, so finally they decided to make the ramp or beginning of the coaster higher.

They tested it again, and it made it up a bit farther up the loop, but was still dropping out.  We discussed the problem some more, but they didn't have enough track to make the coaster any higher.  After more discussion among themselves and some gentle hinting on my part, they decided to make the loop smaller.  

Voila!  It worked!

Another group that had a valuable lesson was the group below.  They built a loop with a 90 degree turn.  I asked at the end of the session if anyone had had any problems to overcome and they said yes.  They first had the track flat and the marble flew off the track.  After some trial and error and thinking on their part, they realized they had to bank the track to get it into the cup!  Good thinking girls!

The biggest challenge of the day, besides the noise (which was all very joyful), was keeping some of the groups from changing their design constantly.  Some groups felt that they had to try every possible design and in the end had nothing to share with the class.  I tried to get the groups to experiment, decide upon a design, get it working and stop to share with the class.  A couple of groups just couldn't stop experimenting, they were having too much fun!  The other challenge was that a couple of groups just wanted to get the marble down the track with no twists or turns, so they needed a little encouragement to try new things, and step out of their comfort zone.

This was a great experience for all of us, students, teachers, parents, and me!

Potential and Kinetic Energy for 4th grade

In January, we went in and worked with the fourth grade on an experiment from teachengineering.org called Falling Water.  In this experiment, you take a straw, a meter stick, colored water, and some paper.  The idea is to test that a water drop falling from 90  cm has more potential and kinetic energy than the same size drop falling from 30 or 60 cm.  This idea is tested by dropping the same amount of water from three different heights.  We chose the heights of 30, 60 and 90 cm.  We marked the straws 1 inch from the bottom and the students tried to get the same amount of water for every test.  We had groups of three and four students run the experiment as a team.  Each team member dropped water from each height.  They then measured the diameter of the water drops and recorded them on a table.

Here are some students dropping the measured water from 90 cm.  You can see the measured amount of water contained in the straw.  It is a stretch for the students to reach 90 cm from the table top, so we suggest that they run it on the floor.  The second photo shows the water after the drop.  You can see it makes a nice large circle on the paper.

The students circle the drops with ink, then record the data in a table.  You can see the paper with the drops circled on the left below and two team members filling out the data table.

The students have a great time with this experiment, and overall the experiment works the way it should with two exceptions.  One, each team member makes a drop at each height.  Some teams are very careful and meticulous and their data is very tight.  Other team or team members may not be as careful about the whole process.   They may not get the same amount of water in the straw each time.  They may have problems with using the straw and keeping the water in, or they may not trelease the water from the straw with it straight up and down and may release it at a slant.  If you drop the water with the straw slanted you get a nice big oval rather than a circle, and then it is hard to pick a diameter.  The other thing that can happen is that some team members are very careful and one or two may not be as careful with the process.  In this case, you will get two good data points, and one or two that may be way off.

Even if the results are not great for every team, it presents a learning opportunity.   We discussed why some of the data point are off.  The table that the students use with sample data is shown below.

	Water height at 30 cm	Water height at 60 cm	Water height at 90 cm
Diameter of first splash	70 mm	68 mm	65 mm
Diameter of second splash	45 mm	65 mm	60 mm
Diameter of third splash	49 mm	57 mm	66 mm
Average Diameter	55	63	63

The writeup asks that the students calculate the total of the drop diameter and the average.  First of all, the fourth grade has not studied averages yet, but some of the more advanced students can do this.  However, I disagree with this method for graphing the data.  If we use the data above, then the graph that results is shown below.  This graph shows that the drop size increases from 30 to 60, but not from 60 to 90.  So, the students could conclude that the height of the drop doesn't necessarily result in a larger circle.







However, if we have the students plot each data point, then we know there are some problems with the data.  We can see right away that the first set of data show that the drop size for two of the students is about 45 to 49, but the third point shows a drop size of 70 mm.  Right away, the students can see that something is not quite right.  It could be that one of the students used too much water, or slanted the straw and then measured the resulting oval with a very large diameter.  In the 60 cm drop, we have one data point that looks correct, but two that look a little large.  The third set of data at 90 cm looks about right.  Having the students plot all of the data rather than just the average shows where there could be problems with the experimental method, and opens up the discussion about how to run careful experiments.  If a student team is very careful, they should see plots such as the one shown for student 3.   Most of our students groups had such plots.






Overall, this is a great experiment, and one that I would recommend.  The students love it, and find it straightforward to do and results in a lot of good discussion about experimental method and the care that scientists must take with experiments as well as discussions about potential and kinetic energy.