Unit V: Virtual Simulation Assignment
Pendulum Lab
Objectives:
4. Apply the concept of momentum conservations to daily life.
4.1 Investigate the momentum conservation in simple pendulum motion.
5.Identify the total mechanical energy conservation.
5.1 Explain the total energy conservation in simple harmonic motion.
5.2 Relate the mass and speed of the pendulum to kinetic energy and potential energy.
Case L[m] M[kg] Angle
a 0.5 0.5 10
b 0.5 1.5 10
c 1 0.5 10
d 1 1.5 10
We are going to explore simple harmonic motion through the Pendulum Lab provided by PheT to find out the relationship between the mass of the bob, the length of the string, the period of the pendulum, and the total energy of the system with respect to the released angles. You will record the period T and the vertical distance difference H in the Excel spread worksheet (in the highlighted area) for eight cases.
Open the “Pendulum Lab” Interactive Simulation. After accessing the website, click on “Lab”.
Click on “Velocity” and “Energy Graph” in the top left. Click on “Ruler” and “Period Timer” in the bottom left (See green oval). You can move along the ruler and the period timer when necessary.
For “Gravity” and “Friction” on the second box from the top right, leave the values as 9.81 m/s2 and none.
Let’s explore Case A first. Set the length as 0.5 meters and the mass as 0.5 kg in the top right. Adjust the angle as 50 degrees, and watch how the KE (Kinetic Energy) and the PE (Potential Energy) vary at the Energy Graph as well as the change of the velocity vector on the bob. You may click on the “slow” button at the bottom for detailed changes. Notice that the velocity is 0 when the pendulum is at the highest position and the velocity is at its maximum value when the pendulum is at the lowest position. That is, the total mechanical energy is the KE at the lowest position and is the PE at the highest position.
Click on the play button (see the red arrow in the screenshot below) on the “Period” box and wait a little bit to find the measurement of the period T of the pendulum. Enter the value on the provided Excel spreadsheet.
Using the ruler, you need to measure the vertical distance difference H when the pendulum is at the lowest position and the pendulum at the highest position. Freeze the moment when the pendulum is at the lowest position using the “slow” button and the “pause” button. If you cannot catch the exact desired moment, you may click on the nearest possible moment.
Find the vertical distance from the bottom of the screen to the center of the blue bob. The total length of the ruler is 100 cm. The number is 20 at the center of the bob. So, the vertical distance is 100 – 20 = 80 cm at the lowest position.
Resume the motion of the pendulum to find the highest position. After finding that position, measure the distance from the bottom to the center of the blue bob using the ruler. It shows 2 cm at the center of the bob, but it may be slightly different from person to person due to measurement error. So, the vertical distance is 100 – 2 = 98 cm at the highest position.
Now we can obtain the vertical distance difference H, which is 98 – 80 = 18 cm. Record this data in the provided Excel spreadsheet. Then the total energy E of this system is automatically calculated.
Now move on to the next case, Case B, in which the angle, length, and mass are 50 degrees, 0.5 meters, and 1.5 kg respectively. Click on the red stop button to reset the data. Also, click on the period bar to clear the previous value. Set the length as 0.5 meters and the mass as 1.5 kg in the top right. Make sure that the angle is set to be 50 degrees, the acceleration due to gravity is 9.81 m/s2, and no friction. Repeat the process above to find the period T and the vertical distance difference H in this case.
Repeat the above processes for the remaining cases. After completing the table, answer the Unit V Assignment questions.
