Answer:
2.96 cm
Step-by-step explanation:
By Hook's law
Force(F) = Spring constant(k) × Extension(d)
F = k × d
Force is the weight of the object, F = W = mg
So we get, mg = kd ⇒ m ∝ d
2.5 ∝ 1.68 --------------(1)
4.4 ∝ d' --------------(2)
From (1) & (2), 4.4/2.5 = d'/1.68
d' = 2.96 cm ⇒ the required extension.