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Lesson 1 Energy Flow in Technological Systems

  Energy in Many Forms

Energy exists in many forms, and you have learned about some of the most common types of energy in this lesson.


C1.23 power lines and wind turbine in field
Many different natural and technological systems use energy and energy conversions. You should have an appreciation for these systems and know how to detect the presence of energy, predict energy conversions, and describe different forms of energy. In the next lesson, we will look at how changes in system energy can indicate work has been done.

  Virtual Lab

Energy Conversion in a System © Explore Learning


Work through this activity to observe the law of conservation of energy in action. The activity has you work with a device similar to Joule’s heat apparatus that was used to measure the mechanical equivalent of heat.

In the Gizmo, a suspended cylinder has gravitational potential energy. When the cylinder is released, the gravitational potential energy is converted into kinetic energy, which causes the stirrer in the water to spin.


Procedure:

  1. Open the Gizmo by clicking on the link or accessing the Online Resources for Print Students section in your online course.
  2. What is the initial temperature (T) of the water (found in the upper left corner of the simulation)?

  3. Click on the play button ( ). What happens as the cylinder drops?

    The propeller in the water spins, and the temperature of the water increases.
  4. What is the final temperature of the water?

    29.69°C
  5. Why do you think the temperature of the water increased?

    The kinetic energy of the propeller was converted into heat energy.

    Activity A:
    Potential Energy and Height
    		Get the Gizmo ready:
    • Click the reset button ( ).
    C1.24 Cylinder at 800 m

      The raised cylinder in the Gizmo has gravitational potential energy (GPE) because gravity can cause the cylinder to drop. When the cylinder drops, its kinetic energy is converted into heat energy, which raises the temperature of the water.

    1. How do you think increasing the cylinder’s height will affect the final temperature of the water?

      Predict. Your answer cannot be wrong.
    2. Gather data: Make sure the water’s mass is 1.0 kg, its temp is 25°C, and the cylinder’s mass is 5 kg. Set the cylinder’s height to 100 m. (Note: The large height scale used by the Gizmo, while not practical in a real-world experiment, makes it easier to produce observable temperature changes in the water.)

      Click on the play button and record the water’s final temperature in the table below. Repeat the experiment at each cylinder height to complete the second column in the table below.

      Calculate: Subtract the water’s initial temperature from its final temperature to complete the third column of the table.

      An object’s Ep can be calculated by multiplying its height (h) by its mass (m) and acceleration due to gravity (g): Ep = mgh. On Earth, g = 9.81 m/s2. Calculate the cylinder’s Ep for each of the trials you completed and fill in the last column of the table.

      Cylinder Height (m)
      		Final Temp. (°C)
      		Change in Temp. (°C)
      		Cylinder Ep(J)
      100


      200


      500


      1 000



      Cylinder Height (m)
      		Final Temp. (°C)
      		Change in Temp. (°C)
      		Cylinder Ep(J)
      100 26.17 1.17
      		 4 900
      200 27.34 2.34 9 800
      500 30.86 5.86 24 500
      1 000 36.72 11.72 49 000
    1. How does doubling the height of the cylinder affect its Ep?

      It doubles the Ep.

      How does doubling the cylinder’s Ep affect the change in temperature experienced by the water?

      It doubles the temperature change.

      Activity B:
      Potential Energy and Mass       		Get the Gizmo ready:
      • Click the reset button. ( ).
      C1.25 Temperature and mass chart

    1. How do you think increasing the cylinder’s mass will affect the final temperature of the water? Explain your prediction.

      Predict and explain. Your answer cannot be wrong.
    1. Gather data: Make sure the water’s mass is still set to 1.0 kg and its temp is 25°C. Set the cylinder’s height to 500 m.

      Use the Gizmo to complete the second column of the table below and then calculate the change in temperature and the cylinder’s Ep for each trial.

      Cylinder Mass (kg)
      		Final Temp. (°C)
      		Change in Temp. (°C)
      		Cylinder Ep(J)
      1


      2


      5


      10



      Cylinder Mass (kg)
      		Final Temp. (°C)
      		Change in Temp. (°C)
      		Cylinder Ep(J)
      1 26.17 1.17 4 900
      2 27.34 2.34 9 800
      5 30.86 5.86 24 500
      10 36.72 11.72 49 000

    1. Describe any patterns you see and compare your results with the results you got when experimenting with the cylinder’s height in activity A.

      Just as with doubling the cylinder’s height, doubling its mass causes the cylinder’s gravitational potential energy to double. As the gravitational potential energy of the cylinder doubles, the change in temperature experienced by the water doubles.