â Must-know
Further detail
đ A higher-power motor lifts the same mass in a shorter time, whereas a lower-power motor takes longer.
â Must-know
đ In a closed system, energy cannot be created or destroyed, so the total energy remains constant.
Further detail
The five listed energy stores are:
Lubrication can reduce unwanted energy transfers by reducing friction.
Insulation can reduce unwanted energy transfers by reducing the rate of thermal energy transfer.
1. What does power measure?
2. A device transfers 1 joule of energy each second. What is its power?
3. In a closed system, energy moves between stores during a change. What happens to the system's total energy?
What does power measure?
The rate of energy transfer or work done.
What power corresponds to transferring one joule per second?
One watt.
What remains constant in a closed system?
The total energy.
What happens to energy during changes in a closed system?
It cannot be created or destroyed.
Where is energy usually dissipated during system changes?
In the thermal store of the surroundings.
How does energy become less useful during system changes?
It is dissipated and stored in less useful ways.
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