Question

DL6 Physics 7A Activity 2.7 (page 1) Graphically Representing Energy Relationships A) Phenomenon: Falling Ball: Overview: Restate energy conservation; practice graphing energies from rest to just before it hits ground. Assume a 1 kg ball is dropped from a height of 2 meters above the floor. ituation I: We will analyze the energies of a dropped ball at any time between when it is dropped 1) Rethinking and restating energy conservation: Our standard expression of energy conservation for this situation is APE.. AKE-0. There are times, however, when it is more useful to have a different expression of energy conservation (e.g when graphing energies). Your instructor will use the definition of "A". and some algebra, to show how the expression Elat any time) -constant PE, Your TA will illustrate why this is true. + KE is equivalent to APE + AKE-. Whole class discussion 2) Using Energy Conservation to Graph Energies for the Falling Ball: In order to graph the energies (PE, KE, and E) of the dropped ball as a function of height one must decide where physically in space to put y 0. Since PEmgy. where we put y -o will also be where PE,-0. For any given physical situation you can set y 0 wherever you want! We will make a graph for energies for a ball dropped 2 meters above the floor, with y O set 3 m below the floor. a) Based on the choice of y-0 (as depicted in the picture), fill-in the table below. At which location do you know KE? What is E, at all locations? Why? Why does it make sense to find PE, first Eal second, and KE last? Location y (m) PE, KEE 2m Max height floor Middle Floor 3rm y o- b) Plot PE, KE, and Ea of the ball (all on the same graph) as a function of height. Do this by first placing the points from the table on the graph, and then connecting the points. Make sure to not extend the plot outside the range where the ball is physically present. Be prepared to explain how you constructed your graph. Whole class discussion Continue to Next Page Unit 2: Applying Models to Mechanical Phenomena 42 DL 6

Answer 1