Mechanical Energy and Position
Lesson 6 of 11
Objective: SWBAT identify the relationship between mechanical energy and an object's position through self-collected data.
This lesson is designed to engage students in scientific discourse around mechanical energy and an object's position. By experimenting and collecting data, students will be able to provide evidence for their claims, thus addressing standard SP7 and MS-PS3-2 simultaneously.
Which ball will have more speed as it moves down the ramp? Ball A, B, or C?
Explain how you know or why you think A, B or C.
After 3-4 minutes, I ask two to three students to share their responses with the whole class. If any student does not agree, I ask them to share their reasoning.
For the next section, I use the PhEt demonstration used in the prior lesson, Mechanical Energy and Mass. If each of your students have access to a device with flash, they can run the demo themselves. Because we use iPads in the classroom, they do not have flash, and so I run the demo using my laptop and the SMARTBoard.
While observing the demonstration, I ask students to answer the following questions in order to guide their thinking:
Where does the skater have the MOST potential energy?
Where does the ball have the MOST potential energy?
Which, skater or ball, had more speed while moving down the ramp?
- Why do you think this?
After the demo is run, I give the kids an additional 3-4 minutes to finish writing down their thoughts in their notes sheets. Then, I ask the kids to share their answers with their shoulder partners (person sitting closest to their right shoulders) and compare responses.
After the demonstration, I want the students to reflect on their original thoughts in the beginning of class and compare those to what they think now. I have them respond to the following prompt:
I think that the higher an object is, the ….. an object’s mechanical energy is. Explain why you think this, using information from the demonstration.
After a few minutes, I ask students to share their responses with their table mates.
Now, students will actually test their thinking by doing a hands on activity using the carts and ramps. To do the activity, you will need the following materials per team: 1 cart, 1 ramp, tape, measuring tape, calculator.
Students follow the procedure on their notes sheet and record their data (distance travelled, time it took) and calculate the speed for each release point.
I am moving around from group to group ensuring proper following of the procedure and also asking questions like:
What have you noticed so far about the different release points?
Has the car moved faster or slower as you move the release point higher?
After the activity, it's important for students to use this data to help them form their thinking about mechanical energy and position. To do this, I have them answer the following questions in their notes sheet:
Which cart had the most potential energy? How do you know?
Which cart had the most kinetic energy? How do you know?
- By increasing (making more) the height of the cart, what did you do to the amount of mechanical energy?
It's important for students to include evidence from their activity and from the demonstration to support their answers. This will help to address SP7 and also make them better writers because the are practicing supporting their thoughts with concrete examples and evidence.