Lab # 6_Conservation of Energy

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St. Cloud Technical and Community College *

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1300

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Mechanical Engineering

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Dec 6, 2023

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Courtesy: Trish Loblein, www.phet.colorado.edu PHYS: 1305 Conceptual Physics Lab # 6 – Conservation of Energy Saint Cloud Technical and Community College St. Cloud, MN 56303 ===================================================================== Lab Partner: ___________________ Lab Partner: __________________________ Learning Goals: Students will be able to: ❖ Explain the Conservation of Mechanical Energy concept using kinetic and gravitational potential energy. ❖ Design a skate park using the concept of Mechanical energy. ❖ Describe Energy -Pie, -Bar, and -Position Charts from position or selected speeds. ➢ Explain how changing the Skater affects the situations above. ➢ Explain how changing the surface friction affects the situations above. ❖ Predict position or estimate of speed from Energy -Pie, -Bar, and -Position Charts ❖ Look at the position of an object and use the Energy -Pie, -Bar, and -Position charts to predict direction of travel or change in speed. Set-up: Please go to https://phet.colorado.edu/en/simulation/energy-skate-park OR enter “ PhET Skatepark ” key word in any search engine ( for example; Google, Bing, etc.).

Courtesy: Trish Loblein, www.phet.colorado.edu Part: I 1. Investigate what affects the skater’s path and discuss your ideas with your partner. You should try adding some track, changing shapes or building jumps . (There is no friction on the track. Paste your snippet below and provide description. For your reference, sample data is provided in the first row. [20 Points] Adding track: (I started with the first U shaped track and then added another U shaped track to it): When the skater first started, they had total potential energy because they were up high. As they reached the bottom of the first U shaped track, they had all kinetic energy. As they reached the top of the first peak, ¾ of their energy was potential and ¼ was kinetic. At the bottom of the second U shaped track, they had about half potential and half kinetic energy. As they slowed at the top of the last peak before they went backwards through the track again, they had less and less kinetic energy and more potential energy. Potential energy is proportional to height, so the higher the skater was in the track, the more potential energy they had. I selected the V shape track, and I started skating from the right to the left. When the skating happened, the skater had a potential energy because I started from the top going down. As it reached the bottom of the V shape track it had all kinetic energy. When the skater reached the other top peak ½ of there anergy was potential and ¼ was kinetic energy. I selected the W shape track. I started from the left top and made the skater go all the way to the other side of the W. when the skater went down there was potential energy. As it reached to the first U shape track it had kinetic energy. As it reached to the first peak ¾ of their energy was potential and ¼ was kinetic. At the bottom of the second U shaped track, they had about half potential and half kinetic energy.

Courtesy: Trish Loblein, www.phet.colorado.edu 2. Explain how you could use your investigation to plan a track that is fun, challenging and one that is relatively safe. You might think for example, when does he: fly off an end? Make it to the top a hill? Or land a jump? [ 5 Points] - To make it fun and challenging, the skater started high ad run down to a loop with very high speed and go up to a high hill and run down the track to the ground to finish. It will be safe because the loop is not too high, and they started high enough that their speed enough to go on a loop and go to a very high hill and come back down to the ground safely. 3. Build a good track and sketch it (provide snippet of it). Then use the Energy Graphs to study the Skater’s energy and provide answer to the following questions. [20 Points] • Decide which graphs or chart best helps you understand what makes your track successful

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Courtesy: Trish Loblein, www.phet.colorado.edu - The potential energy graph and kinetic energy graph are helpful to understand conservation of mechanical energy. • Look in your text to find out what the Conservation of Mechanical Energy means and explain it in your own words. - Conservation of mechanical energy is a principle that means that the total mechanical energy in a system remains constant as long as the only forces acting are conservative forces. The mechanical energy in a system will remain the same if there isn’t any o ther force acting on it except conservative force. • Explain why your track is successful in terms of Conservation of Mechanical Energy. Include drawings of the Chart or Graphs to help explain your reasoning. NOTE: You may include snippet instead of drawing. - The track is successful because in the track there is up and down or a loop and each of these comes with a transition between kinetic and potential energy. It doesn’t have any friction in the track. Which means that at any point in the ride the total mechanical energy is the same. This is a result of the conservation of mechanical energy. 4. Using the Law of Conservation of Mechanical Energy, explain what things need to be considered when designing any successful track. [5 Points] - When designing any successful track, the length, steepness, the weight limit of the skater and presence of friction all need to be considered. Moreover, I need to consider the potential energy and the kinetic energy the skater needs. And make sure that they are not equal at all time but equal once they experience fluctuation. We also have to make sure that the total amount of energy has to always remain the same. To prevent any dangerous accidents happening and make the track fun and safe.

Courtesy: Trish Loblein, www.phet.colorado.edu Part: II 1. Josie made a frictionless hot wheel track that looks like the one shown. She placed a dog skater on the left top of track at 1. [30 Points] a. Make a data table like the one below b. Fill in the Prediction column by sketching what you think the Pie chart will look like for the ball at points 1-4. NOTE: You can draw predicted graph on a piece of paper, take picture of it, and paste it in the provided space. c. Use the Loop Track with the Dog Skater to test your ideas and make any adjustments Pie chart Prediction Simulation Explain differences 1 After running the simulation, it was confirmed that the skater had mostly all potential energy at point 1 on the track. My predictions were almost correct. 2 I thought there will be more kinetic and there was actually more potential. 3 There was a lot of kinetic and I was somewhat right. 2 1 3 4

Courtesy: Trish Loblein, www.phet.colorado.edu 2. Pretend that Josie can magically change the dog to different things like the simulation can. [15 Points] a. What do you think would change about the Pie Charts? - The percentage for each component b. Explain why you think the charts would similar or different. - The starting point makes a different in the results. c. Check your reasoning using the simulation and make corrections if necessary. - All the reasoning is right and that will not need any correction. 3. Josie has a friend, Phillip that can magically change the friction on the track like the simulation can. [15 Points] a. What do you think would change about the Pie Charts? - In the friction on the track is changed, the pie charts will change. there will be and additional energy called thermal energy and as a result the contribution of Kinetic and potential energies and the pie chart decreases as the time goes. b. Explain why you think the charts would similar or different. - Similar, because the friction would give off different results. c. Check your reasoning using the simulation and make corrections if necessary. - There will be no change because they are similar. 4. Work with your partner to build a track and sketch it. [15 Points] a. Make a table like the one you did for question 1. Predict what you think the charts will look like. b. Use the simulation to check your ideas. c. Test your ideas from questions 2 and 3. Make changes to your answers if necessary. NOTE: For this table you need to change the mass of an object and you need to use the friction force. d. 4 I was right on more potential energy but not how much. Prediction Simulation Explain differences 1 Kinetic energy:10% Potential energy: 85% Kinetic energy:5% Potential energy: 95% There is no motion and not a lot of friction causing there to be almost no kinetic nor thermal energy. However, there is a lot of potential energy since the ball is located at a tall height.

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Courtesy: Trish Loblein, www.phet.colorado.edu 5. Explain how you can use what you understand about pie charts to predict bar charts. [5 Points] - Slice to illustrate numerical proportion. in a pie chart, the arc length of each slice is proportional to the quantity that represents. a bar chart or a bar graph is a chart or a graph that presents category data with rectangular bars with heights or length proportional to their values that they represent. Therefore, multiply the decimal version of the percentage to fine the amount it would be on the bar graph. Thermal Energy:5% Thermal energy:0% 2 Kinetic energy: 90% Potential energy: 5% Thermal energy: 5% Kinetic energy: 70% Potential energy: 20% Thermal energy: 10% There is a lot of kinetic energy since the skater just went downhill. however, there is almost no potential energy since there is no height left to fall from. The thermal energy is low as well since the potential energy dropped. 3 Kinetic energy: 45% Potential energy: 45% Thermal energy: 15% Kinetic energy:40% Potential energy: 40% Thermal energy: 20% Both the kinetic and potential energy are equal to each other. This is due to the fact that there is a lot of motion going on from the skater going down the hill. Potential energy increased since the skater is about to go down a hill (height increased). Thermal energy increased due to the increase of kinetic energy. 4 Kinetic energy: 50% Potential energy: 30% Thermal energy: 20% Kinetic energy: 47% Potential energy: 20% Thermal energy: 33% Kinetic energy increased only a bit because the skater had been going down a hill previously. Potential energy decreased since height is barely being gained. Thermal energy increased because going uphill creates requires force.

Courtesy: Trish Loblein, www.phet.colorado.edu 6. Sketch this track and label where the 5 spots could be. [25 Points] a. He is at his maximum speed (A) b. He is stopped (B) c. He is going his average speed (C) d. He is going slow (D) e. He is going fast (E) NOTE: Replace X with your answer such as A, B, C, D, or E from the above options 7. Sketch this energy-position graph and label where you think the same 5 spots are. [25 Points] a. Test your ideas using the Double Well Roller Coaster track. b. If one of your friends in the class asked you for help making sense of this type of graph, what would you say? - I would explain why my graph looks like that and show her how it works. Like where is the potential energy is located and where is the kinetic energy is located and stat plotting the points based on where it goes fast, max, slow, and average speed. NOTE: You may copy yellow boxes from above question and paste here at appropriate place. - The energy increases as the slope of the coaster becomes steeper. And as the roller coaster goes up in position the energy decreases. E D A C B

Courtesy: Trish Loblein, www.phet.colorado.edu 8. Talk about how you could use the Energy - Pie, -Bar, and -Position charts to predict direction of the ball is rolling. [20 Points] a. Check your ideas using the simulation. - Suppose the bass is moving down the inclined plane the total energy chart will be straight line or constant, the potential energy chart will be straight line with negative slope, for kinetic energy it will be vise versa position slope. b. Talk about how you could tell if the ball is going to be moving faster, at the same speed, or slower? - If the ball is at a slope that is steep going in the negative direction it will move faster if the track is on a flat surface, the ball is going to move the same. If the track is at a steep slope, going in the positive direction, the ball will move slower. c. Pretend you are writing a test for this unit. Type a question that includes at least one type of graph and a Skater on a different track. Then, give it to another group to see if they can predict the direction and changing speed of the ball. Make sure to attach your question. - Analyze a single wall graph and determine the velocity at the five spots.

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