Teacher Notes



Teacher Notes
Publication No. 12512
PSWorks™ Conservation of Energy TracksStudent Laboratory KitMaterials Included In Kit
Catching Curve
Metal balls, ¾" diameter, 2 PSWorks™ Conservation of Energy Tracks Support rod, metal Additional Materials Required
Pencil
PSWorks™ Support Stand, or support stand and clamp Ruler or meter stick Safety PrecautionsThe materials in this laboratory activity are considered safe. Please follow all normal laboratory safety guidelines. DisposalThe materials should be saved and stored for future use. Lab Hints
Teacher Tips
Correlation to Next Generation Science Standards (NGSS)^{†}Science & Engineering PracticesDeveloping and using modelsUsing mathematics and computational thinking Planning and carrying out investigations Obtaining, evaluation, and communicating information Constructing explanations and designing solutions Disciplinary Core IdeasMSPS2.A: Forces and MotionMSPS3.A: Definitions of Energy MSPS3.B: Conservation of Energy and Energy Transfer MSPS3.C: Relationship between Energy and Forces MSETS1.A: Defining and Delimiting Engineering Problems MSETS1.B: Developing Possible Solutions HSPS2.A: Forces and Motion HSPS3.A: Definitions of Energy HSPS3.B: Conservation of Energy and Energy Transfer HSPS3.C: Relationship between Energy and Forces Crosscutting ConceptsEnergy and matterCause and effect Scale, proportion, and quantity Systems and system models Performance ExpectationsMSPS31: Construct and interpret graphical displays of data to describe the relationships of kinetic energy to the mass of an object and to the speed of an object. Sample Data{12512_Data_Table_1}
Answers to Questions
Recommended Products


Student Pages


Student PagesPSWorks™ Conservation of Energy TracksIntroductionExamine the concept of conservation of energy. Show that when an object falls, the path the object takes does not affect its change from potential energy to kinetic energy. Concepts
BackgroundThe law of conservation of energy states that energy cannot be created or destroyed—only converted between one form and another. In order to raise a ball to the release point at the top of an inclined plane, one must exert energy. Work, another term for energy, is being performed on the ball in order to raise it. Work is defined as a force used through a distance. It requires work to move any object. If a force used on an object does not make the object move, such as pushing on a brick wall, then no work is performed. The energy used to raise an object, such as a ball, to a position higher than a reference height is “stored” in the ball—the ball is said to have potential energy (PE). This potential energy may be used at a later time to do work. The potential energy of the ball is related to its height and weight. In general, potential energy is equal to the weight of an object, which equals the mass (m) times the acceleration due to gravity (g), times the relative height (h) of the object (see Equation 1 and Figure 1). {12512_Background_Equation_1}
{12512_Background_Figure_1}
As the ball begins to move down the inclined plane, the potential energy is converted into kinetic energy (energy of motion). For a rolling ball, two types of motion are involved—the ball travels in a straight path down the inclined plane and it rotates. Therefore, the ball has both linear kinetic energy and rotational kinetic energy. Linear kinetic energy (KE_{l}) is related to the mass (m) and linear speed (v) of the ball (Equation 2). Rotational kinetic energy (KE_{r}) is related to the moment of inertia (I) of the ball about the rotational axis and the rotational speed (ω; the lowercase Greek letter omega) of the ball (Equation 3). The total kinetic energy (KE_{T}) of the ball is equal to the linear kinetic energy plus the rotational kinetic energy (Equation 4).
{12512_Background_Equation_2}
{12512_Background_Equation_3}
{12512_Background_Equation_4}
In this demonstration, the ball will roll down a track without slipping. The point on the ball in contact with the surface of the track will be instantaneously at rest with respect to the track. The frictional force between the surface of the rolling object and the surface of the track acts against, and balances, the force due to gravity pulling the object down. Since no slipping occurs between the two surfaces, energy will not be dissipated or lost as heat and all the potential energy the ball has at the top of the track will be converted into kinetic energy at the bottom (Equation 5).
{12512_Background_Equation_5}
Therefore, the ball will have the same energy at the bottom of the track that it has at the top of the track. It does not matter what path the ball takes, as long as the relative change in height is the same, the kinetic energy at the bottom will equal the potential energy at the top.
Materials
Catching Curve
Metal ball, ¾" diameter Pencil PSWorks™ Conservation of Energy Tracks PSWorks™ Support Stand, or support stand and clamp Ruler or meter stick Support rod, metal Safety PrecautionsThe materials in this laboratory activity are considered safe. Please follow all normal laboratory safety guidelines. Procedure
Student Worksheet PDF 