Passage III

Earth's gravitational field extends both above and below Earth's surface. In Figure 1, both the value of this field, , and the average density, ρ, of matter within Earth are graphed versus distance, r, from Earth's center. In addi­tion, Figure 1 identifies 5 regions, each of which is located either above or below Earth's surface.

Figure 2 shows the percent of Earth's mass located within a given distance r from Earth's center. For example, 10% of Earth's mass is located within 2,300 km of Earth's center, 20% of Earth's mass is located within 2,900 km of Earth's center, and so on.

Figures adapted from A. M. Dziewonski and D. L. Anderson, "Pre­liminary Reference Earth Model."©1981 by Elsevier B.V.

17. Based on Figure 1, the approximate value of Earth’s gravitational field at r = 14,000 km is most likely:

Answer and Explanation

Your Answer is

Correct Answer is C

Explanation

Looking at figure 1, according to the trend of the gE curve, it can be judged that in the atmosphere, the larger r is, the smaller gE is;

So when the abscissa r is 14000 km, it can be speculated that gE should be less than 13000 gE at km, so it should be less than 2.5; but according to the slope of the curve at this time, gE will decrease by less than 1 for every 1000 km increase in r, so gE at 14000 km will not be less than 1.5. The range should be between 1.5-2.5