Question Detail
Question
A piece of wood with a density of 706 kg/m³ is tied with a string to the bottom of a water-filled flask. The wood is completely immersed, and has a volume of 8.00 × 10⁻⁶ m³. What is the tension in the string?
Correct Answer
Option B is the correct answer.
Detailed Explanation
The wood is less dense than water (1000 kg/m³), so it wants to float. The string holds it submerged. Tension = Buoyant force - Weight. Buoyant force = ρ_water × V × g = 1000 × 8.00×10⁻⁶ × 9.8 = 0.0784 N. Weight = ρ_wood × V × g = 706 × 8.00×10⁻⁶ × 9.8 = 706 × 7.84×10⁻⁵ = 0.0554 N. Tension = 0.0784 - 0.0554 = 0.0230 N.
Hint
Tension = buoyant force - weight when object is held submerged and wants to float upward.