Most students will have an intuitive sense that kinetic energy depends on how fast something is moving (speed) and how massive it is (mass). (We use speed instead of velocity, because energy is a scalar, and independent of direction.) They know that it hurts more in dodge ball when the ball is thrown with more speed than when it is thrown with less speed. They also know that is hurts more to drop a bowling ball on their foot than it does to drop a tennis ball. Exactly how mass, speed and kinetic energy are related is the purpose of this lab. Which is more important in determining kinetic energy? mass or speed? or are they of the same importance?
The equation for Kinetic Energy, KE = mv2 is based on Newtonian mechanics. Advanced students may extrapolate this equation from the data collected during this activity, all students are encouraged to try to find the mathematical relationship. Newtonian mechanics works well for the everyday objects students encounter in this activity. However, Einstein's "Theory of Special Relativity" is needed to understand the last activity, "The Ultimate Kinetic Energy challenge," in this set of three activities. While students do not need a solid understanding of how kinetic energy relates to mass and speed, there are some other concepts they do need to be familiar with. The students need to be able to interpret scientific notation. This is part of the pre-algebra core curriculum. However, students may not be very comfortable using scientific notation, and a concept review prior to conducting the computer investigation might be useful. It is also important that students have some graphing skills. A review of what to do with the independent and dependent variables, and the constants may also be in order.
All teachers have unique and original ways to introduce new topics and ideas. Presented here are a couple of ideas for introducing this lab activity.
As the students conduct the online lab, the role of the teacher should be one of facilitator. Allow students as much freedom as possible. Ideally, they will discover the relationships on their own. It is best if students work in small groups, no more than three students per group. Two is ideal.
The teacher should conduct the lab activity prior to the students. This way the teacher will be able to answer student questions as they arise. Encourage students to read the instructions prior to proceeding to the next page. This will help make the lab easier. While the students are conducting "The Energy of Moving Matter," the teacher may want to encourage the students to try to find two different objects, with energies that are the same or similar. While the students are conducting "Graphing the Energy of Moving Matter," the teacher will need to remind the students to hold mass constant and vary the speed, then hold the speed constant and vary the mass.
Depending on classroom constraints it may be useful to have a class discussion after completing "The Energy of Moving Matter," and before beginning "Graphing the Energy of Moving Matter" Use the questions at the end of the lab as a starting point for the discussion. This may be a good time to review graphing.
These two activities may take up to 4 classroom periods, depending on technical problems and skill of students. It is worthwhile to discuss any possible technical problems with the technical specialist prior to beginning the lab. Such problems may include: whether or not all students have network access, the number of available computers with internet access, whether or not the local server is up and running on the day you wish to conduct the lab.
A student lab packet is provided that includes student instructions, tables, graph paper, and the questions from the lab. Teachers may wish to use this for classes that need extra support, or for classes with time constraints, or merely to facilitate the ease of conducting the investigation.
Now that the students have been able to quantify the relationship between mass, speed and kinetic energy, conduct a second discussion similar to the one in the "Invitation to Learn" activity. Ask the students to look at their previous answers. Ask "how have your views changed?" "What do you know now that you didn't before?" This time the students should be able to say "It depends on the speed of the tennis ball..." Ask the students to write a paragraph answering the previous questions.