Which of the following is most nearly the mass of the Earth? (The radius of the Earth is about 6.4 × 106 m)
A. 6 × 1024 kg
B. 6 × 1027 kg
C. 6 × 1030 kg
D. 6 × 1033 kg
E. 6 × 1036 kg
(GR9277 #19)
Solution:
F = mg = GMm/r2
M = gr2/G
M = 9.8 × (6.4 × 106)2 / (6.67 × 10−11)
≈ 10 × 6 × 1012+11
= 6 × 1024
Answer: A
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