This chapter of The Physics Classroom tutorial ties together the concepts of work, power, and the Law of Conservation of Energy. Six interactive tutorials explore kinetic and potential energy, power, mechanical energy, and the relationship between energy and forces. It also gives students practice in calculating work and using energy bar charts. f
6-8: 4E/M2. Energy can be transferred from one system to another (or from a system to its environment) in different ways: 1) thermally, when a warmer object is in contact with a cooler one; 2) mechanically, when two objects push or pull on each other over a distance; 3) electrically, when an electrical source such as a battery or generator is connected in a complete circuit to an electrical device; or 4) by electromagnetic waves.
6-8: 4E/M4. Energy appears in different forms and can be transformed within a system. Motion energy is associated with the speed of an object. Thermal energy is associated with the temperature of an object. Gravitational energy is associated with the height of an object above a reference point. Elastic energy is associated with the stretching or compressing of an elastic object. Chemical energy is associated with the composition of a substance. Electrical energy is associated with an electric current in a circuit. Light energy is associated with the frequency of electromagnetic waves.
9-12: 4E/H1. Although the various forms of energy appear very different, each can be measured in a way that makes it possible to keep track of how much of one form is converted into another. Whenever the amount of energy in one place diminishes, the amount in other places or forms increases by the same amount.
9-12: 4E/H9. Many forms of energy can be considered to be either kinetic energy, which is the energy of motion, or potential energy, which depends on the separation between mutually attracting or repelling objects.
9-12: 4E/H10. If no energy is transferred into or out of a system, the total energy of all the different forms in the system will not change, no matter what gradual or violent changes actually occur within the system.
Next Generation Science Standards
Disciplinary Core Ideas (K-12)
Conservation of Energy and Energy Transfer (PS3.B)
Conservation of energy means that the total change of energy in any system is always equal to the total energy transferred into or out of the system. (9-12)
Energy cannot be created or destroyed, but it can be transported from one place to another and transferred between systems. (9-12)
Mathematical expressions, which quantify how the stored energy in a system depends on its configuration (e.g. relative positions of charged particles, compression of a spring) and how kinetic energy depends on mass and speed, allow the concept of conservation of energy to be used to predict and describe system behavior. (9-12)
Relationship Between Energy and Forces (PS3.C)
When two objects interact, each one exerts a force on the other that can cause energy to be transferred to or from the object. (6-8)
Crosscutting Concepts (K-12)
Energy and Matter (2-12)
The transfer of energy can be tracked as energy flows through a natural system. (6-8)
The total amount of energy and matter in closed systems is conserved. (9-12)
Changes of energy and matter in a system can be described in terms of energy and matter flows into, out of, and within that system. (9-12)
Energy cannot be created or destroyed—it only moves between one place and another place, between objects and/or fields, or between systems. (9-12)
NGSS Science and Engineering Practices (K-12)
Using Mathematics and Computational Thinking (5-12)
Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses to using algebraic thinking and analysis, a range of linear and nonlinear functions including trigonometric functions, exponentials and logarithms, and computational tools for statistical analysis to analyze, represent, and model data. Simple computational simulations are created and used based on mathematical models of basic assumptions. (9-12)
Use mathematical representations of phenomena to describe explanations. (9-12)
%0 Electronic Source %A Henderson, Tom %D December 12, 2004 %T The Physics Classroom: Work, Energy, and Power %V 2015 %N 31 March 2015 %8 December 12, 2004 %9 text/html %U http://www.physicsclassroom.com/Class/energy/
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