Questions 4-5
The magnitude of the Earth’s gravitational force on a point mass is F(r), where r is the distance from the Earth’s center to the point mass. Assume the Earth is a homogeneous sphere of radius R.
What is}{F(2R)} "\frac{F(R)}{F(2R)}")
?
A. 32
B. 8
C. 4
D. 2
E. 1
Gravity force: F = GMm/R2 → F ∝ 1/R2
F(R) ∝ 1/R2
F(2R) ∝ 1/4R2
F(R) / F(2R) = 4R2/ R2 = 4
Answer: C
The magnitude of the Earth’s gravitational force on a point mass is F(r), where r is the distance from the Earth’s center to the point mass. Assume the Earth is a homogeneous sphere of radius R.
What is
A. 32
B. 8
C. 4
D. 2
E. 1
(GR9277 #04)
Solution:
Gravity force: F = GMm/R2 → F ∝ 1/R2
F(R) ∝ 1/R2
F(2R) ∝ 1/4R2
F(R) / F(2R) = 4R2/ R2 = 4
Answer: C
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