Unit 5 Review Short Answer (Chapter 19, 20, 21)

What are the two major motions of Earth as it travels through space?

Answer explanation

The two major motions are rotation and revolution.

Which of the Earth's motions causes day and night?

Answer explanation

Rotation causes day and night.

What causes the seasons?

Answer explanation

The tilt of Earth's axis as it revolves around the sun causes the seasons.

What are solstices and equinoxes? How are they related to the seasons?

Answer explanation

A solstice occurs when the sun is farthest north or south of the equator (the longest and shortest days of the year).

During an equinox, the noon sun is directly over the equator (day and night are exactly the same).

Solstices mark the beginnings of summer and winter; equinoxes mark the beginnings of fall and spring.

How would the seasons be different if Earth were not tilted on its axis?

Answer explanation

There would be no seasons. Temperatures would remain fairly constant year-round at any given location.

What is the law of universal gravitation?

Answer explanation

The law of universal gravitation states that every object in the universe attracts every other object.

What two factors determine the force of gravity between two objects?

Answer explanation

The masses of the objects and the distance between them determines the force of gravity.

Suppose the moon were closer to Earth. How would the force of gravity between the Earth and the moon be different?

Answer explanation

The force of gravity would increase if the moon and the Earth were closer.

What two factors act together to keep Earth in orbit around the sun?

Answer explanation

Inertia and gravity act together to keep Earth in orbit around the sun.

Why doesn't Earth simply fall into the sun?

Answer explanation

Earth doesn't fall into the sun because the Earth's inertia causes it to tend to move in a straight line.