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Questions and Answers
A student is analyzing the energy transfers in a car engine. The engine converts chemical energy from fuel into kinetic energy to move the car, but also produces significant amounts of thermal energy due to friction and heat. Considering the principles of energy conservation, which statement accurately describes the complete energy transformation?
A student is analyzing the energy transfers in a car engine. The engine converts chemical energy from fuel into kinetic energy to move the car, but also produces significant amounts of thermal energy due to friction and heat. Considering the principles of energy conservation, which statement accurately describes the complete energy transformation?
- The total chemical energy from the fuel is completely converted into kinetic energy, making the engine highly efficient.
- The engine destroys a portion of the chemical energy to produce kinetic energy and mitigate overheating.
- The total energy in the system remains constant, with the chemical energy from the fuel being transformed into a combination of kinetic and thermal energy. (correct)
- The kinetic energy produced by the engine is greater than the initial chemical energy due to the engine's amplification of energy.
A crane lifts a heavy steel beam vertically. Analyze the energy transfers occurring during this process, focusing on the relationship between work done and energy stores, neglecting air resistance. Which of the following statements correctly relates the work done by the crane and its impact on the energy stores?
A crane lifts a heavy steel beam vertically. Analyze the energy transfers occurring during this process, focusing on the relationship between work done and energy stores, neglecting air resistance. Which of the following statements correctly relates the work done by the crane and its impact on the energy stores?
- The work done by the crane is equal to the gravitational potential energy gained by the steel beam, with no change in kinetic energy. (correct)
- The work done by the crane is entirely converted into kinetic energy of the steel beam, increasing its velocity as it rises.
- The work done by the crane is partially converted into gravitational potential energy and partially dissipated as thermal energy due to the crane's internal friction.
- The work done by the crane is less than the gain in gravitational potential energy because some energy is lost due to air resistance.
In a closed system, a chemical reaction occurs, releasing heat and causing the system's temperature to rise. Which of the following best describes the energy transfers and stores within the system?
In a closed system, a chemical reaction occurs, releasing heat and causing the system's temperature to rise. Which of the following best describes the energy transfers and stores within the system?
- Chemical energy is converted into kinetic energy, increasing the overall movement of molecules, and the total energy of the system increases.
- Chemical energy is converted into thermal energy, increasing the internal energy store of the system, and the total energy of the system remains constant. (correct)
- Thermal energy is converted into chemical energy, decreasing the internal energy store of the system, while the total energy of the system remains constant.
- Chemical energy is converted into thermal energy, increasing the internal energy store of the system, while the total energy of the system decreases.
Flashcards
Energy
Energy
The capacity for doing work; it exists in different stores and can be transferred, dissipated, or stored.
Energy Transfer
Energy Transfer
The movement of energy from one form to another; examples include heating, waves, electric currents, or force moving an object.
Energy Transfer Diagrams
Energy Transfer Diagrams
Diagrams illustrating energy flow within a system, showing energy stores as boxes and transfers as arrows.
Study Notes
- Energy exists in different 'stores'.
- Energy cannot be created or destroyed.
- Energy can be transferred, dissipated, or stored in different ways.
- Energy can remain in the same store for millions of years or just a fraction of a second.
- Energy transfers occur continuously whenever a system changes.
- A system change involves altering the way energy is stored
Examples of Energy Transfers:
- A boat moving through water transfers chemical energy into kinetic energy.
- Boiling water in an electric kettle: electricity increases the internal energy of the element, which in turn increases the internal (thermal) energy of the water, raising its temperature.
- A swinging pirate ship ride transfers kinetic energy into gravitational potential energy.
Types of Energy Transfer:
- The potential difference (voltage) of a supply measures the energy given to charge carriers in a circuit, with units in volts (V).
- Voltage facilitates electric current flow between two points.
- Energy is emitted by a material, reducing its internal energy.
- Infrared radiation from the Sun emits energy into space.
- 'Work' signifies energy transfer, as seen in a grazing cow, a firing catapult, or a boiling kettle.
Diagrams for Showing Energy Transfer:
- Transfer diagrams use boxes for energy stores and arrows for energy transfers.
- A transfer diagram of a child at the top of a slide shows gravitational energy transforming into kinetic and internal energy due to mechanical work and friction.
- Sankey diagrams illustrate how energy in a system is transferred into different stores.
- Sankey diagrams are especially useful when the amount of energy in each source is known.
- The width of the arrow in a Sankey diagram is proportional to the amount of energy.
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