Answer: 20N
Explanation:
According to Newton's law of gravitation which states that every particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers
F = Gm1m2/r^2
Where
F = force between the masses
G universal gravitational constant
m1 and m2 = mass of the two particles
r = distance between the centre of the two mass
Therefore, weigh of an object on earth is inversely proportional to the square of its distance from the centre of the earth
W₁/W₂ = r₂²/r₁²
W₂ = W₁r₁²/r₂²
W₁ = 180 N
r₁ = R
r₂ = 3R
W₂ = (180 × R²)/(3R)²
W₂ = 180R²/9R²
W₂ = 180/9
W₂ = 20N
its weight at 3R is 20N
