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Home  >>  JEEMAIN and AIPMT  >>  Physics  >>  Class11  >>  Gravitation
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Suppose universal gravitational constant starts to decrease, then

a)length of year will increase b)kinetic energy of earth will increase c)earth will follow spiral path d)all the above
Can you answer this question?

1 Answer

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$T^2= \large\frac{4 \pi ^2}{GM}$$R^3$
$\therefore$ Time period will increase as G decreases.
Kinetic energy $=\large\frac{GMm}{2R}$
Kinetic energy decreases as G decreases
Hence a is the correct answer.
answered Aug 30, 2013 by meena.p
edited Jul 3, 2014 by lmohan717
T2 = 4R3π2/GM from kepler's law. Thus, T increases with decrease in G, thereby increasing the length of the year.
KE of earth = (1/2)MR2W2 = 2π2MR2/T2. From kepler's law, R3 is proportional to T2 AND hence KE is inversely proportional to T2/3. As G decreases T increases and increase in T decreases the KE.
The radius of the path around the sun is proportional to T3/2. Thus if G decreases, T increases and hence R increases and earth will follow a spiral path

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