GED Science TestPhysical ScienceMedium
A student is investigating the properties of a non-Newtonian fluid by mixing cornstarch and water. They observe that the mixture acts like a solid when a sudden force is applied, but flows like a liquid when left undisturbed. Which property of the fluid is primarily responsible for this observed behavior?
- ASurface Tension
- BDensity
- CViscosity
- DCapillarity
Show answer & explanationAnswer & explanation
Correct answer: C. Viscosity
The change in resistance to flow (from liquid-like to solid-like) under stress is a characteristic of how viscosity behaves in non-Newtonian fluids.
Why the other options are wrong
- A. Surface tension is the cohesive force at the surface of a liquid, not its bulk flow behavior.
- B. Density is mass per unit volume and doesn't explain the change in flow behavior.
- D. Capillarity is the ability of a liquid to flow in narrow spaces against gravity, unrelated to this phenomenon.
Non-Newtonian Fluid Viscosity
A fluid whose viscosity (resistance to flow) changes depending on the applied shear stress or strain rate, unlike Newtonian fluids where viscosity is constant.
- Can become more or less viscous under stress.
- Examples include cornstarch and water (oobleck), ketchup, and paint.
- Behaves like a solid when hit hard, but flows like a liquid when poured slowly.
Memory trick: Fluid's flow tells its story, especially under stress.