Suppose universal gravitational constant starts to decrease, then

Options

A. length of the day on the earth will increase
B. length of the year will increase
C. the earth will follow a spiral path of decreasing radius
D. kinetic energy of the earth will decrease

Answer

B, D

Explanation

If universal gravitational constant `G` starts to decrease, then gravitational force between the Sun and the earth will also start to decrease. Therefore, the earth will try to follow a path of larger radius. Hence, its period of revolution round the Sun will increase. Therefore, duration of the year will increase. But rotational motion of the earth about its own axis will remain unchanged, hence period of rotation unchange. Hence, option a is incorrect, b is correct and c is correct.
Since the radius of the circular path of the earth will increase or the earth will follow a spiral path of increasing radius, therefore its `PE` will increase but `PE` is always negative , so the magnitude of `PE` will decrease. Hence, `KE` will also decrease.
Therefore, option d is correct.