Earth's Rotation and Revolution: Practice Problem Solutions

1. Rotation is Earth spinning on its axis; revolution is Earth traveling around the Sun.

2. About 24 hours for one rotation (a day); about 365.25 days for one revolution (a year).

3. West to east. So the Sun appears to rise in the east and set in the west.

4. Earth turns 360 degrees in 24 hours, which is 15 degrees per hour, so each hour of time corresponds to about 15 degrees of longitude.

5. The swing direction slowly turned relative to the floor, showing that the Earth itself was rotating beneath the pendulum.

6. About 30 km/s (about 107,000 km/h).

7. A year is about 365.25 days, not exactly 365. A leap day every four years keeps the calendar in step with the seasons.