Gravitation Question 123
Question: The mass of the earth is $ [6.00\times 10^{24},kg] $ and that of the moon is $ [7.40\times 10^{22},kg] $ . The constant of gravitation $ [G=6.67\times {{10}^{-11}},N-m^{2}/kg^{2}] $ . The potential energy of the system is $ [-7.79\times 10^{28},joules] $ . The mean distance between the earth and moon is [MP PMT 1995]
Options:
A) $ [3.80\times 10^{8},metres] $
B) $ [3.37\times 10^{6},metres] $
C) $ [7.60\times 10^{4},metres] $
D) $ [1.90\times 10^{2},metres] $
Show Answer
Answer:
Correct Answer: A
Solution:
$ [U=-\frac{GMm}{r}] $ $ [\Rightarrow ,7.79\times 10^{28}] $ $ [=\frac{6.67\times {{10}^{-11}}\times 7.4\times 10^{22}\times 6\times 10^{24}}{r}] $ $ [\Rightarrow ,,r=3.8\times 10^{8},m] $
