Read Fluids: Separate Rotating Surfaces from Outflow
Fluid questions often combine geometry with Bernoulli or hydrostatic balance. State whether the fluid is rotating steadily or draining through an opening before selecting an equation.
Fluid Surfaces and Efflux is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Start with the condition
A rotating free surface has z proportional to r².
Build the governing relation
Use the relevant height measured vertically from the free surface to the outlet, not the total tank dimension.
Finish with a physical check
Check the limiting case before selecting an option: remove the special feature in the diagram or make the relevant parameter very large or very small. The result should reduce to a familiar relation.
OlympIQ exam lens
- ✓State the physical condition before choosing a formula.
- ✓Keep direction, sign and constraint information explicit.
- ✓Test one limiting case before committing to an option.
A rigidly rotating liquid has no flat free surface; treating it as static misses the centrifugal pressure variation.
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