Skate Park Energy Revisited

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Objective

Students determine how friction and the shape of the ramp impact the transformation of potential into kinetic energy.

Big Idea

The total energy of a system is conserved as the energy changes from one form to another.

Context and Supplies

This activity builds off the first Skate Park Energy lesson where students first apply the conservation of energy to a skate park simulation. In this lesson, students use a computer simulation to explore how differently shaped ramps impact the energy transformations from potential to kinetic energy and what impact friction has on the energy transformations. This is a guided inquiry activity where students go through a series of simulations and construct their own understanding and conclusions. 

This involves the application of NGSS HS-PS3-2; students also apply engineering performance HS-ETS1-4. This is a guided inquiry activity so Science Practice 1: Asking questions (for science) and defining problems (for engineering) is applied as is Science Practice 5: Using mathematics and computational thinking and Science Practice 7: Engaging in argument from evidence as students use computations to support their conclusions. 

Do Now Hypothesis - Does the Shape of the Ramp Matter?

5 minutes

The lesson starts with the do now power point projected on the white board. Students are to draw this picture in their notebooks and write their answer to the question. This is a strategy which activates students thinking on a topic. In this case, students think about the impact of differently shaped ramps on a balls velocity at the bottom. "Common sense" tells most students that a steeper ramp results in a faster speed at the bottom. However, this is not the case. Energy is conserved so since both spheres have the same starting potential energy they both have the same kinetic energy as the bottom of the ramp and thus have the same exit speed from their respective ramps. The only difference is that the ball on the steeper ramp will make the trip faster. I don't reveal the answer to the students. Instead, I return to this concept at the end of class after they have had a chance to test the idea on the simulator. 

How Does the Shape of Ramp Impact Energy Transfer?

25 minutes

I start with a demo of the PhET simulator so that students navigate to the right place and see the settings and features that are used. PhET provides a series of high quality physical science simulators and is provided by The University of Colorado. 

The goal is to test out the idea introduced in the opening. Does the shape of a ramp affect the final speed of the skater at the bottom?

Students are to get in groups of 2-3 and they can choose their own partners. This tends to create homogeneous groups which is appropriate. This is a guided activity where students are given a structure to work in, but they have choices to make and seek to answer some of their own questions.  

Group collect the skate park activity 2 worksheet and a computer. They then construct three different ramps and start the skater from the same height for each one. They learn that the velocity of the skater at the bottom of the ramp is the same for each ramp. Another test they do with this activity is to determine the impact of friction on the mechanical energy of the skater.

While students are engaged in this activity, I am circulating the room. I clarify any questions they have and also keep an extra worksheet with me and write down the student groups who record exemplary responses so that I can call them up during the debrief period to show the class. 

Skate Park Debrief

20 minutes

Once students complete the worksheet and put the computers away, I display the Do Now - Ramp Hypothesis power point. I ask the question that was posed at the beginning of class: "Does the shape of the ramp impact the speed of the sphere at the bottom?" All students who say NO raise their hands. The expectation is that all of the students accurately assess this situation and predict that the spheres reach the bottom of the ramp with the same speed. 

Then we review the students answers on the energy skate park. I use the document camera and call up the student groups I noted during the activity so they can display their Energy Skate Park - Student Exemplars. If students have conducted the investigation correctly, they can determine that the kinetic energy as the bottom of each ramp is identical. They also know that friction removes mechanical energy from the skater and that the friction turns into thermal energy.

Students are ready to apply conservation of energy to their own roller-coaster design. The next topic deals with how the roller coaster gets its starting energy to begin with... students begin to learn about work and power in the next class.