# 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

$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.
edited Jul 3, 2014
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