A block of wood floats in water with 60% of its volume submerged. In a liquid of density 0.8 g/cm³, the fraction of volume submerged will be: MCQ with Answer and Explanation
A block of wood floats in water with 60% of its volume submerged. In a liquid of density 0.8 g/cm³, the fraction of volume submerged will be:
A. 80%
B. 75%
C. 48%
D. 60%
Answer: Option B
Solution (By JKSSB Mock Tests)
From floatation: ρ_wood/ρ_water = fraction submerged in water = 0.6. Thus ρ_wood = 0.6 g/cm³ (since ρ_water = 1 g/cm³). In new liquid (ρ_l = 0.8 g/cm³), fraction submerged f = ρ_wood/ρ_l = 0.6/0.8 = 0.75 = 75%. This uses the principle that fraction submerged equals density ratio. Memory aid: 'f = ρ_object / ρ_fluid'. Such comparative buoyancy problems test application of Archimedes' principle across scenarios, common in competitive exams. Always maintain consistent units (g/cm³ here simplifies calculation).
Explanation:
g' = g (R/(R+h))². If h=R, g' = g (R/2R)² = g/4. Weight = mg' = mg/4, one-fourth. Above surface, g decreases with square of distance from centre.
Explanation:
Isaac Newton formulated three laws of motion and law of universal gravitation in Principia (1687). He also contributed to calculus, optics. Galileo experiments on motion. Einstein relativity.
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