Tides: Practice Problem Solutions

1. Mainly the Moon's gravity, with a smaller effect from the Sun's gravity.

2. The Moon's pull is strongest on the near side and weakest on the far side, so Earth is stretched along the Earth-Moon line. The ocean bulges on both sides.

3. About 50 minutes later each day, since the Moon moves along its orbit.

4. Spring tides have the highest highs and lowest lows. They occur at new and full Moon, when the Sun, Earth and Moon line up and their pulls add.

5. Neap tides have the smallest range. They occur at first and third quarter Moons, when the Sun and Moon pull at right angles.

6. Alabama's coast has small tides (about 1 to 2 feet), often with only one high tide a day, while the Bay of Fundy has the world's largest tides (up to about 16 m).

7. Tidal friction slows Earth's rotation, making the day slowly longer, and pushes the Moon farther away at about 3.8 cm per year.