What You Need:
- Poster Board/Cardboard
- Construction Paper
- Marbles (various sizes and materials)
- Stopwatch or Clock with second hand
To Do and Observe:
1. Stack the blocks one top of one another. Make sure that they are balanced on a flat surface.
2. Lean the poster board on the blocks so that it forms a ramp like structure.
3. Release a marble from the top of the ramp. Use the stopwatch to observe the time that it takes the marble to travel from the top to the bottom.
4. Continue testing the travel time of the other marbles that you have. Is there a relationship between the size of the marble and the travel time? Does the larger marble travel faster or slower than a smaller marble? How do you think we could slow down the travel time of the marbles?
5. Pick one the marbles to use in the next part of the experiment.
6. Using the materials supplied, alter the ramp so that it slows the marble down by at least 5 seconds.
What's Going On:
In this experiment we have set up a ramp. A ramp or inclined plane is an example of one of the six types of simple machines. A simple machine allows you to use less force to push or pull an object over a greater distance. When using simple machines we can also look at the potential and kinetic energy of the marble. When the marble is at the top of the ramp it has high potential energy, also known as stored energy. As the marble travels down the ramp is builds kinetic energy, or energy in motion. Where do you think that the marble would have the greatest kinetic energy? The marble will have the greatest amount of kinetic energy when it reaches the bottom of the ramp because it would continue to gain energy as it travels down the ramp. Objects that have different masses usually have different amounts of potential and kinetic energy and will also take different times to travel down the ramp. What kind of relationships can you draw that compares the size and masses of the marble to the time that it took to travel down the ramp?
In the second part of the activity participants are challenged to alter the ramp so the marble’s travel time is slowed down by at least 5 seconds. This is essentially a design challenge. There are many ways to alter the ramp so that the needs of the challenge are met. The most common design is to elongate the path that the marble has to travel by creating tracks that go side to side down the ramp. As strategically placed obstacles are positioned on the ramp, the direction and speed of the marble changes as it travels downward. The ramp height also affects the speed of the marble.
In place of the marbles, spherical shaped candies can be used, such as peppermint balls or any other round candy. Large groups of students can be broken down into smaller groups that could later compete against each other to see whose marble is the last to finish the course. If students are having difficulties with completing the challenge, the picture below is one solution.
To extend the time that it takes for the marble to travel from the top of the marble run to the bottom, create a longer path for the marble to travel. To help students understand this concept, you can relate the marble run to slides. Who would reach the bottom first, a person on a slide that goes from top to bottom, or a person on a slide that spirals?
For Older Students To do this activity with older students have them test other variables such as the height of the inclined plane or the angle at which the poster board is positioned. They can also change the material that the marble travels on and discuss the role that friction plays on the speed that the marble travels.