杏吧原创

I read recently that turtles were being "cold-stunned" and sharks were freezing to death in the ocean off the north-eastern US coast. This was due to a cold spell with air temperatures of -12掳C, rather than the average 1掳C. Is this particularly cold or within the normal winter range, and how is it possible for animals to be affected in these ways? Also, why do we not see mass freezing of land animals before sea animals are affected, given the relative stability of ocean temperatures?

Does it require more or less effort to push a loaded wheelbarrow over hard level ground than to turn around and pull it? What about when the ground is soft?