“20000 Leagues Under the Sea” Part2 Ch15

Question 1: The North Star has helped sailors in the northern hemisphere navigate.  Is there a South Star?  Did the Southern Cross help mariners find their way?

Question 2: When the Nautilus hits an iceberg Verne describes the collision as involving the disturbance of furniture and wall hanging pictures inside the ship.  Back in chapter 9 the question arose how Captain Nemo secured his furniture etc. when he rammed other ships in vengeance.  Did he have to spend considerable time preparing his ship for war, e.g. packing up his valuables?

Question 3: Who in this chapter said “We may brave human laws, but we cannot resist natural laws?

Question 4: How much pressure can freezing water exert? (e.g. in breaking apart rocks it has frozen in the cracks of, or in bursting water pipes)

see: http://www.newton.dep.anl.gov/askasci/eng99/eng99532.htm

Question 5: Captain Nemo explained why the iceberg had flipped over and trapped them between it and the ice sheet:

…”An enormous block of ice, a whole mountain, has turned over,” he replied.  “When icebergs are undermined at their base by warmer water or reiterated shocks, their center of gravity rises, and the whole thing turns over…”

What physics are involved in objects capsizing like the top-heavy iceberg?

Answer 5:According to “Fundamentals of Physics” Third Edition Extended by David Halliday and Robert Resnick with the assistance of John Merrill, Copyright 1988, published by John Wiley & Sons, Inc. :

The weight of a floating object (acting downward) is balanced by the buoyant force (acting upward).  However, the points of action of these two forces are not the same.  The weight acts at the center of mass of the floating object, the buoyant force acts at the center of mass of the hole in the water, a point called the Center of Buoyancy.



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