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All 15 Flashcards — Storages and flows
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Question
What is a storage (stock) in a system?
Answer
A storage is a place where matter, energy, or information builds up over time (e.g., water in a reservoir, CO2 in the atmosphere).
💡 Hint
Storage = what can build up.
Question
In system diagrams, what do boxes represent?
Answer
Boxes represent storages (stocks) where matter, energy, or information accumulates over time.
💡 Hint
Box = storage.
Question
What is the difference between an input and an inflow?
Answer
An input is the thing that moves (e.g., water). An inflow is the process moving it into a storage (e.g., rainfall).
💡 Hint
Thing vs process.
Question
In an exam, which phrasing is correct: “rainfall is an input” or “rainfall is an inflow”?
Answer
“Rainfall is an inflow.” The water is the input; rainfall is the flow process.
💡 Hint
Say: rainfall = inflow.
Question
What is a flow in a system?
Answer
A flow is the movement of matter, energy, or information into or out of a storage, changing the amount stored.
💡 Hint
Flow = movement that changes storage.
Question
In system diagrams, what do arrows represent?
Answer
Arrows represent flows moving matter, energy, or information into or out of storages.
💡 Hint
Arrow = flow.
Question
What is dynamic equilibrium in a system?
Answer
Dynamic equilibrium occurs when inflows equal outflows, so the storage stays constant even though flows continue.
💡 Hint
Inflow = outflow.
Question
What is an inflow and what does it do?
Answer
An inflow is a flow that enters a storage and increases the amount stored (e.g., rainfall filling a reservoir).
💡 Hint
Inflow = into the box.
Question
What condition creates dynamic equilibrium?
Answer
Dynamic equilibrium occurs when inflows equal outflows, keeping the storage constant.
💡 Hint
Inflow = outflow.
Question
What is an outflow and what does it do?
Answer
An outflow is a flow that leaves a storage and decreases the amount stored (e.g., dam release reducing reservoir water).
💡 Hint
Outflow = out of the box.
Question
What is a buffer in a system?
Answer
A buffer is a storage that absorbs sudden changes in flows, slowing system response and creating time delays.
💡 Hint
Buffer = slows change.
Question
What happens to a storage when inflows are greater than outflows?
Answer
The storage increases because more enters than leaves (e.g., reservoir fills when rainfall exceeds evaporation).
💡 Hint
In > out = storage up.
Question
What is a system boundary and why does it matter?
Answer
A system boundary is an imaginary line separating the system from its surroundings; choosing it affects what inputs/outputs are included and how useful the model is.
💡 Hint
Boundary = what you include.
Question
In system diagrams, how are storages and flows usually shown?
Answer
Storages are shown as boxes and flows are shown as arrows; thicker arrows often represent larger flows.
💡 Hint
Box = storage; arrow = flow.
Question
In “explain using systems” questions, what 4 things should you identify?
Answer
1 storage, 2 inflows, 3 outflows, 4 whether it is in equilibrium or changing.
💡 Hint
Storage + in + out + state.
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