Energy conservation prelab

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William Rainey Harper College *

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201

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Mechanical Engineering

Date

Oct 30, 2023

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pdf

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Uploaded by ColonelOpossumPerson951

Energy Conservation PRELAB Rev. 3/10/22 DLD 1 PRELAB Energy Conservation Objectives Examine energy transformation Equipment Computer with internet access Theory The Work-Energy Theorem states that the sum of all work done by nonconservative forces (friction, tension, air resistance, etc.) is equal to the change in mechanical energy (here E is standing in for any mechanical energy). ∑ 𝑊 𝑁𝐶 = ∆𝐸 Mechanical energy is any type of energy that is dependent on the position or speed of an object. This lab features three types of mechanical energy, spring potential energy (𝑃𝐸 𝑠 = 1 2 𝑘 𝑠 ∆? 2 ) , gravitational potential energy (𝑃𝐸 ? = 𝑚𝑔?) and translational kinetic energy (𝐾𝐸 𝑇 = 1 2 𝑚𝑣 2 ) . Mechanical energy is conserved if there are no nonconservative forces doing work. ∑ 𝐸 𝑖 = ∑ 𝐸 ? To determine the total mechanical energy of a ball shot in the air at any given time, the position and speed of the ball must be measured. To find the energy stored in a spring, the compression or extension of the spring must also be measured. Activity 1: Energy on a Vertical Toss Simulation 1. Open the simulation located at the link given below. http://thephysicsaviary.com/Physics/APPrograms/EnergyOnVerticalToss/ 2. Read the instructions and click “Begin.” In this simulation problem, you m ust use the concept of mechanical energy conservation to calculate the total energy of the vertically launched ball and the maximum height it reaches. 3. Write the appropriate form of the equation for the Work-Energy Theorem (“Big Ugly”) for the situation presented in the simulation. 4. Complete the randomized problem assigned to you, keeping in mind that the gravitational field constant (g) may be changed and the simulation asks for the maximum height in cm. Repeat the simulation until the computer considers your answers correct.

Energy Conservation PRELAB Rev. 3/10/22 DLD 2 PRELAB Activity 2: Energy Transformations 9. Open the second simulation located at the link given below. http://thephysicsaviary.com/Physics/Programs/Labs/EnergyTransformationLab/ 10. Read the directions for the simulation and click “Begin.” 11. You will need to repeat the simulation several times to understand the relationships between the different variables. Trevor, our hockey player, is on a completely frictionless surface so once released from the spring he will coast across the rink at a constant speed . You must use the timer to measure how long it takes Trevor to pass between the two blue lines on the rink. 12. First, examine the relationship between spring constant and speed. The large green arrows will add or subtract 50N/m from k, the small ones will add or subtract 10N/m. Select any value for k and record it in Table 1. Click on Set Trevor. Make sure Trev or’s mass is set to 75kg and pull him back to a distance of 2m by clicking on the green arrow. When the front of the spring is aligned with the 2m mark, it is set correctly. When ready, click the red arrow to start the simulation and “Fire Trevor.” You will need to start and stop the time in the upper left corner of the screen when Trevor crosses the blue lines. When you are satisfied that you have captured his time correctly, record the time in Table 1. 13. Select 3 additional values for k, making sure to explore the entire range of values from 500N/m to 2000N/m. For each trial, keep Trevor’s mass at 75kg and pull him back 2m. Add all of your data to Table 1. Also, be sure to record the distance between the blue lines here ___________________ Table 1: Changing Spring Constant Value of k (N/m) Time between lines (sec) Speed (m/s) 14. Calculate the speed for each of your 4 trials. Remember that the surface is frictionless. Add the results to Table 1. 15. How are spring constant and speed related ? Use the “Big Ugly” to help you describe the exact relationship.

Energy Conservation PRELAB Rev. 3/10/22 DLD 3 PRELAB 16. For your second set of trials, you will be using a single value of the spring constant. Select one and record it here.__________ 17. Click on “Set Trevor” and set his spring compression to 0.5m. Fire Trevor and collect the appropriate time information and record it in Table 2. Repeat the process for 3 additional distances ranging up to 3m and add your data to the table. Table 2: Changing Spring Compression Spring Compression (m) Time between lines (sec) Speed (m/s) 18. Calculate the speed for each of your 4 trials and add the results to the table. 19. How are the spring compression and speed related? Again, use the “Big Ugly” to help you describe the exact relationship. 20. For your last set of trials, you will be using the same spring constant but you need to change Trevor’s mass. Click on the blue arrow at the lower left side of the screen and set Trevor’s mass to 40kg. “Set Trevor” and set his spring compression to 2m again. Fire Trevor and collect the appropriate time information and record it in Table 3. Repeat the process for 3 additional masses ranging up to 150kg and add your data to the table. Table 3: Changing Trevor’s Mass Trevor’s Mass (kg) Time between lines (sec) Speed (m/s) 21. Calculate the speed for each of your 4 trials and add the results to the table. 22. How are the mass of Trevor and his speed related? Here again, use the “Big Ugly” to help you.

Energy conservation prelab

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