phy1004l. - lab 8- energy of a tossed ball

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0MIAMI DADE COLLEGE/North Campus PHY1004/PHY2053/PHY2048 Diego Cely Garifullina Leysan Monica Camargo Tereza M Gago March 22, 2013 Lab 8: Energy of a Tossed Ball When a juggler tosses a bean ball straight upward, the ball slows down until it reaches the top of its path and then speeds up on its way back down. In terms of energy, when the ball is released it has kinetic energy, KE. As it rises during its free-fall phase it slows down, loses kinetic energy, and gains gravitational potential energy, PE. As it starts down, still in free fall, the stored gravitational potential energy is converted back into kinetic energy as the object falls. If there is no work done by frictional forces, the total energy will remain constant. In this experiment, we will see if this works out for the toss of a ball. M o tio n D etector In this experiment, we will study these energy changes using a Motion Detector. OBJECTIVES Measure the change in the kinetic and potential energies as a ball moves in free fall. See how the total energy of the ball changes during free fall.

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PHY1004L. - Lab 8- Energy of a Tossed Ball

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0MIAMI DADE COLLEGE/North CampusPHY1004/PHY2053/PHY2048Diego Cely Garifullina LeysanMonica CamargoTereza M GagoMarch 22, 2013

Lab 8: Energy of a Tossed Ball

When a juggler tosses a bean ball straight upward, the ball slows down until it reaches the top of its path and then speeds up on its way back down. In terms of energy, when the ball is released it has kinetic energy, KE. As it rises during its free-fall phase it slows down, loses kinetic energy, and gains gravitational potential energy, PE. As it starts down, still in free fall, the stored gravitational potential energy is converted back into kinetic energy as the object falls.If there is no work done by frictional forces, the total energy will remain constant. In this experiment, we will see if this works out for the toss of a ball.

In this experiment, we will study these energy changes using a Motion Detector.objectives Measure the change in the kinetic and potential energies as a ball moves in free fall. See how the total energy of the ball changes during free fall.

Materials Computer Vernier computer interface Logger Pro Vernier Motion Detector Basketball and Wire basketPreliminary questionsFor each question, consider the free-fall portion of the motion of a ball tossed straight upward, starting just as the ball is released to just before it is caught. Assume that there is very little air resistance.1.What form or forms of energy does the ball have while momentarily at rest at the top of the path?While momentarily at rest at the top of the path, the form/forms of mechanical energy the ball has is Potential Energy2.What form or forms of energy does the ball have while in motion near the bottom of the path? While in motion at the bottom of the path, the form of mechanical energy the ball has is Kinetic Energy3.Sketch a graph of velocity vs. time for the ball.4.Sketch a graph of kinetic energy vs. time for the ball.5.Sketch a graph of potential energy vs. time for the ball.

The Shaded region of our graph (above) represent the interval while the ball is in freefall because

6.If there are no frictional forces acting on the ball, how is the change in the balls potential energy related to the change in kinetic energy? The change in the balls potential energy is equal to the change in kinetic energy.Procedure1.Measure and record the mass of the ball you plan to use in this experiment.For this experiment we take the standard weight of the basketball: 0.45kg2.Connect the Motion Detector to the DIG/SONIC 1 channel of the interface. Place the Motion Detector on the floor and protect it by placing a wire basket over it. 3.Open the file 16 Energy of a Tossed Ball from the Physics with Vernier folder.4.Hold the ball directly above and about 1.0 m from the Motion Detector. In this step, you will toss the ball straight upward above the Motion Detector and let it fall back toward the Motion Detector. Have your partner click to begin data collection. Toss the ball straight up after you hear the Motion Detector begin to click. Use two hands. Be sure to pull your hands away from the ball after it starts moving so the Motion Detector does not pick them up. Throw the ball so it reaches maximum height of about 1.5m above the Motion Detector. Verify that the position vs. time graph corresponding to the free-fall motion is parabolic in shape, without spikes or flat regions, before you continue. This step may require some practice. If necessary, repeat the toss, until you get a good graph. When you have good data on the screen, proceed to the Analysis section.Data Table

Analysis1.Click on the Examine button, , and move the mouse across the position or velocity graphs of the motion of the ball to answer these questions.a. Identify the portion of each graph where the ball had just left your hands and was in free fall. Determine the height and velocity of the ball at this time. Enter your values in your data table. b. Identify the point on each graph where the ball was at the top of its path. Determine the time, height, and velocity of the ball at this point. Enter your values in your data table. c. Find a time where the ball was moving downward, but a short time before it was caught. Measure and record the height and velocity of the ball at that time. d. For each of the three points in your data table, calculate the Potential Energy (PE), Kinetic Energy (KE), and Total Energy (TE). Use the position of the Motion Detector as the zero of your gravitational potential energy.

2.How well does this part of the experiment show conservation of energy? Explain.The law of conservation of energy states that energy is never created or destroyed only converted. This law is known by two different names: (1). The Law of Conservation of Energy" (2)."The First Law of Thermodynamics"Conservation of energy means that the total amount of energy in a closed system remains constant. You can't create energy out of nothing, and you can't destroy it - however, you can convert from one type of energy to another. This includes converting useful energy to unusable energy - but the total amount of energy still remains constant. There is a quantity called energy that is conserved in a closed system. That is to say, if no energy get into a system or gets out, the total amount of energy will remain constant.

In our experiment we observed how the potential energy is turned into kinetic energy.

3.Logger Pro can graph the balls kinetic energy according to KE = mv2 if you supply the balls mass. To do this, choose Column OptionsKinetic Energy from the Data menu. Click the Column Definition tab. You will see a dialog box containing an approximate formula for calculating the KE of the ball. Edit the formula to reflect the mass of the ball and click .

4.Logger Pro can also calculate the balls potential energy according to PE = mgh. Here m is the mass of the ball, g the free-fall acceleration, and h is the vertical height of the ball measured from the position of the Motion Detector. As before, you will need to supply the mass of the ball. To do this, choose Column OptionsPotential Energy from the Data menu. Click the Column Definition tab. You will see a dialog box containing an approximate formula for calculating the PE of the ball. Edit the formula to reflect the mass of the ball and click .5.Go to the next page by clicking on the Next Page button, .6.Inspect your kinetic energy vs. time graph for the toss of the ball. Explain its shape.During free fall, the shape of the kinetic energy vs time graph is a Parabola with a maximum at the end of the curve where the KE reach its higher value: 0.98J7.Inspect your potential energy vs. time graph for the free-fall flight of the ball. Explain its shape.During free fall, the shape of the potential energy vs time graph is a Parabola with a maximum at the higher point where the PE reach its higher value: 0.27J

8.Record the two energy graphs by printing or sketching.

9.Compare your energy graphs predictions (from the Preliminary Questions) to the real data for the ball toss. 10.Logger Pro will also calculate Total Energy, the sum of KE and PE (TE=KE+PE), for plotting. Record the graph by printing or sketching. In our graph a line with the slope approximately equal to zero describes the TE 11.What do you conclude from this graph about the total energy of the ball as it moved up and down in free fall? Does the total energy remain constant? Should the total energy remain constant? Why? If it does not, what sources of extra energy are there or where could the missing energy have gone? DEFINITIONS - Extensions or CONCLUSION1.What would change in this experiment if you used a very light ball, like a beach ball? Because the PE and TE are directly proportional to the mass, the result of them will be smaller. The TE is smaller as well but constant. Energy of the ball will reduce by the factor by which ball mass reduces, but there will be no change in vmax and height attained.2.What would happen to your experimental results if you entered the wrong mass for the ball in this experiment?The results of all energies (PE, KE and TE) change because these are directly proportional to the mass. The PE energy is directly related to position, and the KE is related to velocity. So altering the mass wouldnt really affect our graphs too much, but it would definitely change our total energy3. Definition of Conservation of Energy and its mathematical representation.Energy can be defined as the capacity for doing work. It may exist in a variety of forms and may be transformed from one type of energy to another. However, these energy transformations are constrained by a fundamental principle, the Conservation of Energy principle. One way to state this principle is "Energy can neither be created nor destroyed". Another approach is to say that the total energy of an isolated system remains constant.If only conservative forces are acting, the total mechanical energy of a system neither increases nor decreases in any process. It stay constant-it is conserved. E = KE + PE E = 1/2mv2+mghWhere E is the total mechanical energy, KE is kinetic energy, and PE is potential energy. From this, the equation for conservation of total mechanical energy can be derived:Ei = EforKi + Ui = Kf + UfWhere Ei is total initial mechanical energy and Ef is total final mechanical energy. This shows that the total initial mechanical energy equals the total final mechanical energy for the system. It is because of this phenomenon that a roller coaster is called a coaster. After the initial input of energy to carry the train up the lift hill, the roller coaster simply coasts through the rest of the ride.For an elastic force, conservation of energy:1/2mv12+1/2kx12= 1/2mv22+1/2kx22