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Questions and Answers
A roller coaster car is moving up a slope. As it ascends, its speed decreases. Which of the following statements best describes the energy transfers occurring?
A roller coaster car is moving up a slope. As it ascends, its speed decreases. Which of the following statements best describes the energy transfers occurring?
- Gravitational potential energy is being transferred to kinetic energy, increasing the car's overall energy.
- Kinetic energy is being completely destroyed as it is converted to gravitational potential energy.
- The total energy of the system is increasing as the car moves higher, violating the principle of energy conservation.
- Kinetic energy is being transferred to gravitational potential energy and some energy is dissipated as thermal energy due to friction. (correct)
A student uses an electric kettle to heat water. Which of the following correctly describes the energy transfers in this system?
A student uses an electric kettle to heat water. Which of the following correctly describes the energy transfers in this system?
- The kettle transforms electrical energy into chemical energy, which then heats the water.
- Electrical energy is destroyed by the kettle, causing the water to gain thermal energy.
- Electrical energy heats the element, subsequently increasing the internal energy of the element, which increases the water's thermal energy, raising its temperature. (correct)
- Electrical energy is converted directly into kinetic energy of the water molecules.
A catapult launches a stone. Which sequence of energy transfers best describes this process?
A catapult launches a stone. Which sequence of energy transfers best describes this process?
- Gravitational potential energy of the catapult’s frame converts to kinetic energy of the stone.
- Chemical energy in the catapult transforms into kinetic energy of the stone.
- Elastic potential energy in the stretched catapult transforms into kinetic energy of the stone as it is released. (correct)
- Elastic potential energy in the catapult transforms directly into gravitational potential energy of the stone.
Flashcards
Energy
Energy
The capacity for doing work, existing in different 'stores'. It can be transferred, dissipated, or stored, but never created or destroyed.
Energy Transfer
Energy Transfer
When something is moved from one place to another. This may be people, objects or energy.
Energy Store
Energy Store
The different ways in which energy can be stored, including chemical, kinetic, gravitational potential, elastic potential and thermal stores.
Study Notes
- Energy exists in different 'stores'.
- Energy cannot be created or destroyed.
- Energy can be transferred, dissipated, or stored.
- Energy can remain in the same store for varying durations.
- Energy transfers occur constantly when a system changes, altering how energy is stored.
Examples of Energy Transfers
- A boat moves through water as chemical energy converts to kinetic energy.
- Heating water in an electric kettle involves electrical energy increasing 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 demonstrates the conversion of kinetic energy into gravitational potential energy.
Types of Energy Transfer
- Heating
- By Waves
- Electric current
- A force moving an object
Potential Difference
- The potential difference (or voltage) measures the energy given to charge carriers in a circuit, measured in volts (V).
- Voltage facilitates electric current flow between two points.
- Materials 'give-out' energy, leading to a decrease in their internal energy.
Work
- 'Work' signifies the transfer of energy.
- Examples of 'work' include a grazing cow, a firing catapult, and a boiling kettle.
Transfer Diagrams
- Boxes represent energy stores, and arrows indicate energy transfers.
- A child at the top of a slide exemplifies this: gravitational energy converts to mechanical work, increasing speed and doing work against friction.
- This results in a shift from gravitational potential energy to kinetic and internal energy.
Sankey Diagrams
- Sankey diagrams show how energy is transferred into different stores using arrows that split into multiple points.
- The width of the arrow is proportional to the amount of energy, which is useful when the amount of energy in each of the energy sources is known.
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