Tidal forces will eventually slow the Earth's rotation and move the Moon farther from the Earth, thus keeping the Moon orbiting above one point on the Earth all the time. What is another example of a planetary-body system like this: A moon appears stationary in the sky as seen from one half of the main body, while the moon in question cannot be seen from the other half of the main body

Certain bacteria (such as aquaspirillum magnetotacticum) tend to swim toward the earth’s geographic north pole because they contain tiny particles, called magnetosomes, that are sensitive to a magnetic field. if a transmission line carrying 100 a is laid underwater, at what range of distances would the magnetic field from this line be great enough to interfere with the migration of these bacteria? (assume that a field less than 5% of the earth’s field would have little effect on the bacteria. take the earth’s field to be 5.0 * 10-5 t, and ignore the effects of the seawater.)