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Questions and Answers
A roller coaster car climbs to the peak of its track. Assuming minimal energy loss due to friction, which energy transfer best describes this situation?
A roller coaster car climbs to the peak of its track. Assuming minimal energy loss due to friction, which energy transfer best describes this situation?
- Gravitational potential energy is converted into kinetic energy.
- Kinetic energy is transformed into thermal energy as the car ascends.
- Kinetic energy is converted into gravitational potential energy. (correct)
- Electrical energy from the motor is directly stored as gravitational potential energy.
An electric heater warms a room. Which sequence accurately describes the primary energy transfers involved?
An electric heater warms a room. Which sequence accurately describes the primary energy transfers involved?
- Chemical energy → Electrical energy → Thermal energy
- Thermal energy → Electrical energy → Kinetic energy
- Electrical energy → Thermal energy → Radiant energy (correct)
- Electrical energy → Kinetic energy → Chemical energy
A pendulum swings back and forth. At what point in its swing is the transfer between kinetic and gravitational potential energy most balanced, assuming negligible air resistance?
A pendulum swings back and forth. At what point in its swing is the transfer between kinetic and gravitational potential energy most balanced, assuming negligible air resistance?
- At the highest point of the swing.
- At the lowest point of the swing.
- The transfer is constant throughout the entire swing.
- Midway between the highest and lowest points. (correct)
Flashcards
Energy
Energy
The capacity for doing work, which can be stored, transferred, or dissipated in different ways.
System
System
An object or group of objects.
Energy Store
Energy Store
The different ways in which energy can be stored, including chemical, kinetic, gravitational potential, elastic potential, and thermal energy.
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 millions of years or for a fraction of a second.
- Energy transfers occur when a system changes, altering how energy is stored.
Examples of energy transfers:
- A boat moving through the water converts chemical energy into kinetic energy.
- Boiling water in a kettle converts electrical energy into the internal energy of the element, which then increases 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:
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By heating
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By waves
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Electric current
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By a force moving an object
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Potential difference (voltage) measures the energy given to charge carriers in a circuit, with units in volts (V).
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Energy is 'given out' by the material and the internal energy decreases.
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Doing 'work' scientifically means energy has been transferred.
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Examples: a grazing cow, a firing catapult and a boiling kettle.
Transfer Diagrams
- Used to show energy transfers from one store to another.
- Boxes represent energy stores.
- Arrows represent energy transfers.
- Example: A child at the top of a slide has gravitational energy, which is transferred as mechanical work done to speed up and do work against friction, resulting in a shift of energy from gravitational potential energy to kinetic energy and internal energy.
Sankey Diagrams
- Illustrate how energy in a system is transferred into different stores.
- Useful when the amount of energy in each source is known.
- The width of the arrow is drawn to scale to represent the amount of energy.
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