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Questions and Answers
Consider a scenario where a cyclist is riding uphill. Analyze the energy transformations that occur as the cyclist ascends. Which of the following statements BEST describes the primary energy transfers and stores involved in this process?
Consider a scenario where a cyclist is riding uphill. Analyze the energy transformations that occur as the cyclist ascends. Which of the following statements BEST describes the primary energy transfers and stores involved in this process?
- Elastic potential energy stored in the bicycle's frame is released and transformed into gravitational potential energy, propelling the cyclist uphill with minimal contribution from the cyclist's muscle energy.
- Gravitational potential energy is converted into kinetic energy as the cyclist moves upwards, requiring minimal energy input from the cyclist and resulting in a net gain of energy for the system.
- Chemical energy stored in the cyclist's muscles is transformed into kinetic energy and gravitational potential energy, with some energy inevitably dissipated as thermal energy due to the body's metabolic processes and friction. (correct)
- The cyclist's kinetic energy is directly converted into thermal energy due to friction with the air and road, resulting in a decrease in the cyclist's speed and an increase in environmental temperature.
Both transfer diagrams and Sankey diagrams are tools for visualizing energy transformations. Which statement accurately differentiates Sankey diagrams from transfer diagrams in representing energy flow?
Both transfer diagrams and Sankey diagrams are tools for visualizing energy transformations. Which statement accurately differentiates Sankey diagrams from transfer diagrams in representing energy flow?
- Transfer diagrams are designed to illustrate the efficiency of energy conversions by quantifying energy losses, while Sankey diagrams focus on the sequential order of energy transformations without indicating energy magnitudes.
- Sankey diagrams are simplified versions of transfer diagrams, used for basic energy systems with fewer transfer pathways, while transfer diagrams are employed for complex systems with multiple energy stores and transfers.
- Transfer diagrams are qualitative representations showing energy stores and transfers with arrows indicating direction, while Sankey diagrams are quantitative, using arrow width to represent the magnitude of energy in each transfer pathway. (correct)
- Sankey diagrams are primarily used to depict qualitative energy transfers, showing the types of energy stores and pathways, whereas transfer diagrams quantitatively represent energy flow using proportional arrow widths.
In the context of energy transfer, 'work' is defined scientifically as the process of energy being transferred when a force causes displacement. Considering this definition, in which of the following scenarios is 'work' being done on or by the system described?
In the context of energy transfer, 'work' is defined scientifically as the process of energy being transferred when a force causes displacement. Considering this definition, in which of the following scenarios is 'work' being done on or by the system described?
- A battery-powered torch, switched on and emitting light and heat, is doing 'work' as it converts chemical energy into light and thermal energy. (correct)
- A compressed spring, held in place and storing elastic potential energy, is considered to be doing 'work' by virtue of maintaining a state of potential energy.
- A stationary book resting on a shelf is doing 'work' as it exerts a gravitational force on the shelf, counteracting gravity and maintaining its position.
- A hot iron left to cool down on an ironing board is doing 'work' as thermal energy is gradually dissipated into the surroundings through heating.
Flashcards
Energy
Energy
The capacity for doing work. It exists in different 'stores' and can be transferred, dissipated, or stored in various ways.
System
System
An object or group of objects, where energy transfers and changes occur.
Energy Transfer
Energy Transfer
Movement of energy from one store to another, such as from chemical to kinetic energy.
Study Notes
- Energy exists in different 'stores' and cannot be created or destroyed.
- Energy can be transferred, dissipated, or stored.
- Energy can remain in the same store for varying lengths of time.
- Energy transfers occur whenever a system changes, impacting how 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 raises the internal (thermal) energy and temperature of the water.
- A swinging pirate ship ride transfers kinetic energy into gravitational potential energy.
Types of Energy Transfer
- These include:
- Heating
- Waves
- Electric current
- A force moving an object
Potential Difference
- Potential difference (or voltage) is a measure of the energy given to charge carriers in a circuit, measured in volts (V).
- Voltage between two points causes electric current to flow.
- Energy is 'given out' by a material, decreasing its internal energy; for example, infrared radiation from the Sun emitted into space.
- 'Work' is the scientific term for energy being transferred.
Transfer Diagrams
- These diagrams illustrate energy transfers from one store to another.
- Boxes represent energy stores, and arrows represent energy transfers.
- For a child on a slide: gravitational energy stored at the top converts to mechanical work increasing speed and overcoming friction, resulting in a shift to kinetic and internal energy.
Sankey Diagrams
- These diagrams start as one arrow splitting into multiple, showing how energy is transferred into different stores.
- Useful when the amount of energy in each source is known.
- Arrow width is scaled to represent the amount of energy.
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