Engaging in Guided Scientific Inquiry

I chose to investigate the question: How do different surfaces affect the momentum of marbles? For this experiment, I set up a ramp against the edge of my coffee table. The ramp consisted of a turned over cardboard box with another upturned cardboard box positioned underneath it to close the gap between the edge of the first box and the floor. I set a third box at the end of the ramp to act as a barrier for the marble. I used the cardboard as one testing surface. I also used pieces of felt, foam, and sandpaper as surfaces. I laid the pieces over top of the ramp to test them.

One of the challenges I thought I would face was finding a way to keep the marble in a straight path all the way down the ramp. I thought that with the rougher surfaces, especially, the marble would stray to the side, thus traveling a farther distance. However, the mass of the marble propelled it in a straight line in each trial, so this was not a problem. Another challenge was making sure I hit the start and stop on the stop watch at the exact moment the marble hit the ramp and then hit the barrier at the end of the ramp. I had to do a few practice trials to get it right.

I predicted that the cardboard surface would give the marble the most momentum because of its smooth surface. I also predicted the sandpaper would cause the marble to lose the most momentum out of the materials I used due to its rough surface. From the trials I conducted (See Appendix A), I discovered that the felt most inhibited the momentum of the marble. The sandpaper actually had the second fastest trial which was a surprise to me. This could have been because it was not a particularly thick brand of sandpaper. I would probably repeat this experiment using a rougher, thicker type of sandpaper and compare the results. From the results I concluded the fiber of the felt is what slowed the marble the most. From what I know about forces and momentum, I have to conclude that the felt provided the most amount of friction against the marble. I had to wonder if this is why felt is used on pool tables. Perhaps if the tables were made out of different materials, the balls would fly right off the table.

I think the experiment might have worked better if my ramp was not as steep. I might use a more gradual incline so that the marble would not travel as quickly. I might get more accurate measurements with the stop watch this way. Also, it would be interesting to try the same experiment with different types of balls other than marbles. A plastic ball would cause more friction than a marble because of static.

If I was doing this in a classroom, I would provide my students with a list of questions to choose from just as we were. Then, each group would be doing experiments about a similar concept but exploring different aspects of it. I would probably have the students then present their findings to the class after their experiment so that all the groups can share their discoveries. This would be a good way to incorporate technology into the lesson as the students can present their information in the form of graphs or photo presentations.

I would ask the students to make real world connections with the experiments they did. We could then use those connections to further this assignment turning it into an engineering lesson. For example, if the students discovered that the more friction a surface provides, the slower the momentum and they connect that to the fact that they might not go as fast down a grassy hill than down a paved hill, I might ask them to construct a model racetrack using materials that would be conducive to biking quickly, yet safe to ride on.

I would want students to discover the various forces that are acting on the marble that cause it to gain or lose momentum. I want them to realize what aspects of a material will cause it to cause more friction than another material. Also, I would want them to practice the proper way of going through the process of designing and implementing an experiment.

Appendix A

Time (seconds)
Material	Trial 1	Trial 2	Trial 3	Average
Cardboard	0.65	0.59	0.49	0.577
Felt	0.86	0.79	0.86	0.837
Foam	0.80	0.64	0.65	0.697
Sandpaper	0.75	0.49	0.50	0.580