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SMS 204: Integrative marine sciences II

SMS 204: Integrative marine sciences II. Instructors: E. Boss and MJ Perry. Last week’s homework. Issues: measurements & uncertainties. Class web site: http://misclab.umeoce.maine.edu/boss/classes/SMS_204_2008/Syllabus.htm. Uncertainties: the human factor How are regressions done?.

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SMS 204: Integrative marine sciences II

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  1. SMS 204: Integrative marine sciences II • Instructors: E. Boss and MJ Perry. • Last week’s homework. Issues: measurements & uncertainties. • Class web site: http://misclab.umeoce.maine.edu/boss/classes/SMS_204_2008/Syllabus.htm SMS 204: Integrative marine sciences

  2. Uncertainties: the human factor How are regressions done? Demo: rods in water Amnesty program SMS 204: Integrative marine sciences

  3. Some important concepts from last week: • Hydrostatic pressure- weight of water/area • Continuity V*A=constant SMS 204: Integrative marine sciences

  4. Archimedes's principle: • The buoyancy force is equal to the weight of the liquid displaced by the object. For a floating object: What is the balance of forces for a sinking object? SMS 204: Integrative marine sciences

  5. Center of buoyancy vs. center of gravity: Center of gravity: Center of buoyancy: Center of gravity of displaced fluid. When center of buoyancy is bellow the center of gravity the situation is unstable. Separate centers of gravity and buoyancy allow organisms and plants to orient relative to the gravitational field: e.g. dinoflagellates, kelp. SMS 204: Integrative marine sciences

  6. Buoyancy issues for marine organisms: • Blubber is buoyant (0.7-0.9) • Muscles (1.08) and bones (1.9) are denser than water • Air is buoyant (but compressible, that is buoyancy changes with pressure) Some strategies: • Air in stomach (some sharks). • Swim bladder (many bony fishes, physiologically regulated). • Large oily liver (Sharks). SMS 204: Integrative marine sciences

  7. Energy: • Capacity to do work (force x distance). • Kinetic energy: mv2/2 • Pressure-volume energy: PV • Potential energy: mgh • Other: internal energy, heat. • Conservation of energy per unit mass: • Neglecting viscous forces (which convert energy into heat) • v2/2+gh+P/r=constant (Bernoulli’s principle) SMS 204: Integrative marine sciences

  8. Based on Bernoulli’s principle: How would pressure change along a fluid as it flows through a constriction? Movie clip Demo SMS 204: Integrative marine sciences

  9. Based on Bernoulli’s principle: How can we measure the velocity of a fluid using only pressure? Answer: the pitot tube Direction of flow Flowing fluid Dynamic pressure SMS 204: Integrative marine sciences

  10. Fluid’s ‘head’: energy per unit mass/g. Divided into static, velocity, and pressure head. Friction causes loss of head. Where does the energy go? SMS 204: Integrative marine sciences

  11. Squirting column: SMS 204: Integrative marine sciences

  12. Application: flow above a disturbance (Clams, ripples, houses, etc’). SMS 204: Integrative marine sciences

  13. Buoyancy engines on floats and gliders SMS 204: Integrative marine sciences

  14. Skills: reporting significant figures (see handout) • The number of figures used to describe a quantity suggest the accuracy to which it is known. • In science, stating that • x=1.3 • means that your are confident that • 1.35>x>1.25. • Had you written x=8x103, then it suggests 8500>x>7500 (a 6% uncertainty), while x=8.0x103 means 8050>x>7950 (a 0.6% uncertainty). • ‘Rounding’ is the practice of changing numbers to a close relevant number. SMS 204: Integrative marine sciences

  15. Buoyancy and diving SMS 204: Integrative marine sciences

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