10.10.2: Chapter Questions
- Page ID
- 50281
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- If the mass of the moon were four times what it is, the distance between the Earth and the moon would be twice what it is now. Is this a correct statement? Explain why or why not.
- Describe the imbalance between the centripetal force and the gravitational attraction force at different locations on the Earth’s surface. How is it created?
- Where on the Earth’s surface, in relation to the moon’s direction, is the tide-generating force due to the moon equal to zero?
- Why does the moon exert a greater tide-generating force than the sun, even though the sun’s gravitational attraction at the Earth’s surface is almost 200 times stronger than the moon’s?
- How are diurnal, semidiurnal, and mixed tides different? Why is it important to some sailors to know which type of tide is present in a port that they visit?
- Spring tides and neap tides occur twice each month but are not the same height each month. What variations of the Earth’s orbit around the sun might explain seasonal variations in the tidal range of spring or neap tides?
- Why is the tide wave a forced wave in some places and not in others? Where is it a forced wave, and where is it not a forced wave? Why?
- Why are amphidromic systems not established in all ocean basins? Why do some tidal components in a particular basin form amphidromic systems, whereas other components do not?
- Why are tidal currents in the deep oceans slower than those in coastal waters? Why are deep-ocean tidal currents generally rotary, whereas coastal tidal currents are reversing?
- How are tide tables able to predict the future times and heights of high and low tides? These predictions are generally accurate, but weather conditions can cause the heights and times of high and low tide to be shifted somewhat from those predicted. How can this happen? List and explain more than one possible reason.
Critical Thinking Questions
- What might happen if the mass of the moon doubled? How would the moon’s orbit be affected? How would ocean tides on the Earth be affected?
- Why is the tide wave a shallow-water wave? How would it be refracted as it approached a large island with a wide continental shelf?
- Why is it necessary to build a dam across an estuary to get the greatest possible amount of energy from tidal power? Why couldn’t we just put a number of turbines side by side across the entrance?
- There is a proposal to build a sea-level canal with no locks to connect the Atlantic and Pacific Oceans across the Isthmus of Panama near the existing Panama Canal. Imagine that this canal was built instead across Mexico from the Gulf of America (Golfo de México) and that it was several hundred meters wide and 30 m deep.
(a) Would it affect the nature of the tides in the Gulf of America (Golfo de México)? If so, how?
(b) In the canal itself, would there be tidal-height variations of water level?
(c) Would there be tidal currents? If so, hypothesize what characteristics the tides and tidal currents would have. - Tidal bores are formed when a flood tide moves up an estuary or inlet faster than the speed that a shallow-water wave of tidal wavelength can sustain. When the tide ebbs in such inlets, is there a tidal bore that flows seaward? Explain why such an ebb tide bore does or does not exist.