Lesson 19
Ocean Tides, Tidal Forces

1) If we have tides on Earth (mostly) from the moon's pull on the Earth, why don't we have, at any given location, just one high tide per day -- occurring at the time when the moon is closest to that spot? Why are there two high tides per day at any given spot on the Earth? And, given that there are two, why aren't they exactly 12 hours apart?

2) Suppose we call h the difference in the height of the water (or whatever is on the planet's surface!) between low tide and high tide. Estimate h on the surface of Jupiter, due to the influence of Jupiter's moon Europa. Below are a few useful values, for reference.

Mass of Jupiter	1.90x1027 kg
Mass of Europa	0.478x1024 kg
Radius of Jupiter	69.1x106 m
Jupiter to Europa distance	6.71x108 m

3) If you were plunging headfirst toward a black hole, you would be

1. stretched sideways (across your body) but squished lengthwise (from head to toe)
2. squished sideways (across your body) but stretched lengthwise (from head to toe)
3. stretched both sideways (across your body) and lengthwise (from head to toe)
4. squished both sideways (across your body) and lengthwise (from head to toe)

You may change your mind as often as you wish. When you are satisfied with your responses click the SUBMIT button.

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