Sea water vs. pure water – comparison of specific weight The specific weight of sea water is __________ that of pure water:
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Asame as
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Bless than
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Cmore than
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Dnot comparable
Answer
Correct Answer: more than
Explanation
Introduction:Specific weight (gamma) equals rho * g. Because sea water contains dissolved salts, its density is higher than that of pure water under the same conditions, so its specific weight is higher.
Given Data / Assumptions:
- Comparison at similar temperature and pressure.
- Sea water salinity increases density relative to fresh water.
- g (acceleration due to gravity) is effectively identical for both samples.
Concept / Approach:Since gamma = rho * g and g cancels in the comparison, the fluid with higher density has higher specific weight. Sea water has rho slightly greater than 1000 kg/m^3 (often ~1025 kg/m^3).
Step-by-Step Solution:1) Identify property: specific weight depends on density.2) Sea water's dissolved salts increase rho.3) Therefore gamma_sea > gamma_pure.
Verification / Alternative check:Typical values: pure water ~ 9.81 kN/m^3; sea water ~ 10.06 kN/m^3 at standard conditions, confirming the qualitative conclusion.
Why Other Options Are Wrong:
- Same as: ignores salinity effect.
- Less than: opposite of physical reality.
- Not comparable: they are directly comparable at equal conditions.
Common Pitfalls:Confusing specific gravity with specific weight; forgetting that temperature also affects density (but both compared at the same condition).
Final Answer:more than