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SPH 4U Online Lab - Elastic Materials Purpose - The purpose of this experiment is to examine the Conservation of Energy in an elastic material (spring) and to determine the values of the unknown masses. Introduction - For this experiment, we will be using the PhET simulation - Masses and Springs. This can be accessed via the Link in D2L. "Note that for this experiment, values in the simulation will be given in units such as centimeters and grams. However, ALL values must be converted and expressed in "MKS" units for this report. That is, Length, Mass and Time must be expressed in Meters, Kilograms and Seconds respectively. When you access the Phet simulation, ensure you choose the Lab Scenario from along the bottom of the Viclong Energy Lob screen. Take a few minutes to familiarize yourself with the Spring Constant ! controls. Notice that in addition to the total energy, the graph on the left will show the 3 forms of mechanical energy (kinetic, gravitational potential and elastic) along with the thermal energy of the spring. You can indicate the natural length of the spring and its displacement from that position once a mass has been added to the spring and it is stretched. You can then click and drag the ruler to measure how long the spring is stretched. Damping indicates Masses and Springs PHET : how the oscillating motion is slowed down after a mass is added to the spring. We will strictly deal with motion on Earth, so there will be no need to change the Gravity (g = 9.8 : )- When you are ready to begin the lab, click on the orange reset button in the bottom right to reset the simulation to its original conditions. Procedure: 1. Ensure that you have reset the simulation after familiarizing yourself with the controls. Choose the 100 g (0.1 kg) mass and place it on the spring. Record the displacement of the spring (Ax) in meters. Since the force acting on the mass is due to gravity, the force causing the spring stretch can be determined by F = F, = my. Complete Table 1 in the Observation Section. 2. Repeat Step 1 for the red and blue unknown or ? masses. In this case you can only record the Ax values, as we do not know the masses to calculate . Place these values in Table 2.3. Reset the simulation. Set the damping to None. Place the 100 g mass back onto the spring and allow the simulation to run. You may wish to set it to a slow speed in order to observe the energies. Describe what happens to the kinetic, elastic and potential energies as the mass completes one full cycle of its motion - that is as it goes all the way down to its lowest point and all the way up to its highest point. What happens to the total energy throughout the motion? Place these observations in Table 3. 4. Reset the simulation. This time, run it with damping and the 100 g mass. How does damping effect the 3 forms of mechanical energies? Does it effect the total energy? Answer these questions in Table 4. Observations: Table 1: Table 2: Mass (kg] Ax (m) Mass [kg) Ax (m) F = F = mg red 0.1 blue Table 3: Kinetic Energy Description Elastic Energy Description Gravitational Potential Energy Description Total Energy Description Table 4: Kinetic Energy Description Elastic Energy Description Gravitational Potential Energy Description Total Energy Description Analysis: 1. Using the values in table 1, determine the value for the spring constant k. Ensure you include units. 2. Using the k value you just determined, determine the values of the unknown red and blue masses. Show your calculations and include the units3. If you had determined the k value using a mass other than the 100 g (say a 50 g mass), in what way, if any, would that have affected the k value? 4. Using the energy observations for the undamped motion (Table 3) explain WHY the mechanical energies and total energies behave they way they do. 5. Using the energy observations for the damped motion (Table 4) explain WHY the mechanical energies, thermal and total energies behave they way they do. 6. How does the damping cause the simulation to stop? 7. Why does the gravitational potential energy never go to zero? Conclusion: What were the values of the unknown masses