Analyzing Energy in a Bungee Lab
Procedure:
- Using VideoPoint, open “egg drop2” in the Conservation of Energy folder in “shared.”
- Mark the video (be sure to set the scale (there is a 1.5 meter stick in the video)).
- Copy the data from the data table into Excel.
- In Excel, calculate the vertical velocity of the egg.
- Using the mass of the egg as 74.6 grams, create new columns in Excel to calculate the amount of amount of gravitational potential energy (PEg )in the vertical direction and the kinetic energy in the vertical direction at each location. Make a third column showing the total energy at each location. Make a fourth column showing the energy stored in the rubber band (PEspring).
- Create vertical column graph of vertical KE, PEg and PEspring. Under the series tab, put in the appropriate series labels & choose the y-position data from the data table for the horizontal labels on the graph.
- Create “stacked” column graph of vertical KE, PEg and PEspring. Under the series tab, put in the appropriate series labels & choose the y-position data from the data table for the horizontal labels on the graph.
Data Analysis:
- You will be analyzing the motion of the egg at five locations: 1) at the start, 2) 1/2 way up, 3) at the ground, 4) halfway up and 5) the rebound height.
- Sketch the egg at these locations, leaving room to add velocity vectors and an energy bar graph sketch next to each one.
- Show the manual calculations for vertical KE, PEg, PEspring and Total Energy at each one of these locations.
- Sketch an Energy Bar Graph at each one of these locations, showing TE=KEv+PEspring+PEg.
Questions, Analysis & Conclusions:
Explain your reasoning and cite specific examples as proof of your statement.
- From the stacked graph of KE, PEg and PEspring, what happens to the amount of vertical kinetic energy as the egg travels?
- From the stacked graph of KE, PEg and PEspring, what happens to the amount of gravitational potential energy as the egg falls and rises?
- From the stacked graph of KE, PEg and PEspring, what happens to the amount of potential energy in the spring as the egg falls and rises?
- What happens to the total energy after the egg bounces? Why?
- When the egg has fallen half way, how much has the PEg has been transferred to KE? At what point has one-half of the PEg has been transferred to KE?
- Using your graph, determine the location of the egg when the rubber band begins to stretch (on the way down) and where it is again un-stretched (on the way up).
- Determine the spring constant of the rubber band and explain how you found it.
- Make a graph of Time vs PEspring. Find the slope of the line as the rubber bands stretches on the way down. What does this quantity represent?