How Do Different Surfaces Affect the Momentum of Marbles?

In my experiment, I set up a stack of books six inches high and then connected an additional hardback book as a ramp leaning against the stack. This became the incline which marbles rolled down and the selected surface. Precisely two feet from the bottom of the ramp, a string was laid across the floor surface. The procedure of this experiment was to let go of a marble at the top of the book ramp and record the amount of time it took for the marble to roll down the ramp, across the testable surface, and reach the string. In other words, the velocity of the marble was recorded. In order to capture accurate results, two different marbles (one small and one large) were tested on each of the surfaces. Four different surfaces were used: a smooth laminate countertop, a hard-wood floor, a level, compacted carpet, and a shag rug. Each marble was tested five times on each surface to ensure truthful results.

The mean time (in seconds) of the five tests was calculated and is reported in the results below:

	Small marble	Large marble
Smooth laminate countertop	0.5	0.4
Hardwood floor	0.6	0.5
Compacted carpet	1.0	0.9
Shag rug	Did not reach two feet before stopping	Did not reach two feet before stopping

The speed on both smooth surfaces was nearly half the time it took the marble to reach the two foot marker on the carpet. The conclusion of this experiment is that the more friction a surface area provides against a marble, the less momentum the marble will have. Additionally noted is that the larger the mass of a marble, the greater its speed. These were the results I expected to get based on my knowledge of momentum and friction. I knew that friction works to slow an object down.

The procedure of this experiment went well and provided accurate results. I did have to recruit an assistant (my husband) to help release the marble while I timed it. These jobs were too difficult to perform accurately at the same time.

Changes that could be made to this experiment in order to get different results would be to alter the plane of the ramp, use cars or other rolling objects instead of marbles, and test the procedure on still more various surfaces. I would also be interested to see if the difference in the time of the small and large marbles would increase if the distance to the target or string was increased.

I think my students would have fun setting up this experiment in my classroom. The materials used are all basic classroom supplies. Students could decide on something about the experiment to change and see how the results would be different. In order to make this more engaging for my class, I would have to relate it to something they would be interested in. Maybe, I would have them design a new slide for the playground. Depending on how fast or slow they like going down slides, they would have to determine what kind of material to use to make the slide.

All in all, if my students learn that friction affects the momentum of an object by slowing it down, the goal will have been reached. Truthfully, I would be happy that my students could successfully participate in a guided inquiry experience in which they have to be creative and problem solve!