The force of gravity between two objects is given by:

where
G is the gravitational constant
m1 and m2 are the masses of the two objects
r is their separation
In this problem, the mass of the object is

, while the Earth's mass is

. Their separation is

, therefore the gravitational force exerted on the object is
Since the current is inversely propotional to its resistance, when the voltage is doubled the current will be one-half
We have: K.E. = mv² / 2
here, m = 4 Kg
v = 9 m/s
Substitute their values into the expression:
K.E. = (4)(9)² / 2
K.E. = (4)(81) / 2
K.E. = 324 / 2
K.E. = 162 Joules
In short, Your Answer would be 162 J
Hope this helps!