Making Moon Craters
As a weighted plastic egg is dropped into a tub of flour, students see the effect that different heights and masses of the same object have on the overall energy of that object while observing a classic example of potential (stored) energy transferred to kinetic energy (motion). The plastic egg's mass is altered by adding pennies inside it. Because the egg's shape remains constant, and only the mass and height are varied, students can directly visualize how these factors influence the amounts of energy that the eggs carry for each experiment, verified by measurement of the resulting impact craters. Students review the equations for kinetic and potential energy and then make predictions about the depths of the resulting craters for drops of different masses and heights. They collect and graph their data, comparing it to their predictions, and verifying the relationships described by the equations. This classroom demonstration is also suitable as a small group activity.
A "moon crater" made by dropping a weighted. plastic, egg-shaped "asteroid" into a container of flour.Copyright 2013 Jeff Kessler, University of California Davis
This activity models a real-world situation—asteroids hitting the moon's surface—providing students with an example of how engineers and other researchers often employ simple models to help predict how systems behave. By gaining exposure to the fundamental energy equations and initial experimental data, students are able to predict the expected outcome of different egg-drops and compare to experimental results. They learn what engineers know, that energy is influenced by the mass of an object and the height from which that object is dropped. Engineers use their understanding of the energy equations as they create new products, tools, systems and structures that are safe, robust and reliable.
After this activity, students should be able to:
- Predict how the potential energy of a system will change if the height of an object changes.
- Predict how the potential energy of a system will change if the mass of an object changes.
- Predict how the kinetic energy of a system will change if the velocity of an object changes.