Basic fluid types: A fluid with zero viscosity (no internal friction) is called a/an ________.

Introduction / Context:
Idealizations simplify analysis and provide bounds for real behavior. An ideal fluid is one such construct: it has zero viscosity and is incompressible (in many treatments). Although no real fluid is perfectly ideal, the concept is useful for deriving basic relations like Bernoulli's equation.

Given Data / Assumptions:

• Definition-focused conceptual question.
• Viscosity is the property of interest.

Concept / Approach:
A real fluid has finite viscosity; an ideal fluid is assumed to have none. Newtonian fluids obey τ = μ * du/dy with constant μ, while non-Newtonian fluids have μ that depends on shear rate; neither implies μ = 0. Therefore, a fluid with zero viscosity is an ideal fluid in the classical sense.

Step-by-Step Solution:

Verification / Alternative check:
Bernoulli's equation in its most basic form assumes inviscid flow—an idealization consistent with the notion of an ideal fluid.

Why Other Options Are Wrong:

• Real fluid: Always has some viscosity.
• Newtonian fluid: μ constant but not zero.
• Non-Newtonian fluid: μ varies with shear rate; not zero in general.

Common Pitfalls:
Assuming “Newtonian” implies inviscid; it does not.

Final Answer:
ideal fluid