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A force of 200N acts between two objects at a certain dis...

A force of 200N acts between two objects at a certain distance apart. The value of the force when the distance is halved is

A.

400N

B.

200N

C.

100N

D.

800N

Correct answer is D

let the masses of the two objects be M1 and M2
and their distance apart = r

Therefore the force acting F1 = GM1M2r2

for a new distance of r/2, we have a force of

F2 = GM2M2r/2Thus F1×r2=GM1M1andF2×(r/2)2=GM1M1Since GM1M1=GM1M1F1×r2=F2×(r/2)2Therefore 200×r2=F2×r2/4F2=4×200×r2r2=800N