In jet outflow devices, compare jet contraction between two types of mouthpieces. Even though the angle of deviation of the liquid is larger for an internal (re-entrant/Borda) mouthpiece, the contraction of the issuing jet is:

Introduction / Context:
Mouthpieces are short tubes fitted to an orifice. Two common types are the internal (re-entrant, often called Borda mouthpiece) and the external (short cylindrical) mouthpiece. A key behavioural difference is the extent of jet contraction (how much the actual jet area reduces relative to the physical opening). Understanding this helps in predicting discharge and energy losses.

Given Data / Assumptions:

• Internal (re-entrant) mouthpiece causes the flow to turn sharply and separate internally.
• External mouthpiece allows the jet to form outside and may run free or full depending on pressure conditions.
• Coefficient of contraction Cc qualitatively indicates the degree of contraction (smaller jet area means stronger contraction).

Concept / Approach:
In a re-entrant mouthpiece, the jet forms a pronounced vena contracta immediately at the plane of the orifice and the effective jet area is significantly reduced compared with the opening. In contrast, the short external mouthpiece tends to have a fuller jet and less contraction when running full due to wall-guided flow.

Step-by-Step Solution:
Identify flow deflection: internal mouthpiece requires a larger turn → stronger separation.Separation intensifies contraction → smaller effective jet area.Hence, contraction is greater for the internal mouthpiece than for the external one.

Verification / Alternative check:
Typical experimental data show lower discharge coefficient for the Borda (internal) mouthpiece compared to a short external mouthpiece running full, consistent with a stronger contraction in the internal type.

Why Other Options Are Wrong:
Less in the internal mouthpiece: contradicts separation-driven contraction.Equal contraction: ignores geometric and flow-path differences.None of these: unnecessary; the correct comparative statement is available.

Common Pitfalls:

• Confusing discharge coefficient with contraction alone; while related, Cc, Cv, and Cd differ.
• Assuming all short tubes behave like sharp-edged orifices.

Final Answer:
more in the internal mouthpiece