BuoyancyHardQuestion 30980
Question
A block of wood (mass 100 g, density 500 kg/m³) is held submerged in water (density 1000 kg/m³). Force needed to hold it is (g = 10 m/s²):
- A1 N upwardCorrect
- B1 N downward
- C0 N
- D2 N upward
Correct answer
1 N upward
Explanation
Volume = 100g/500 = 200 cm³ = 2×10⁻⁴ m³. Buoyancy = 1000×10×2×10⁻⁴ = 2 N. Weight = 0.1×10 = 1 N. Net upward force = 2−1 = 1 N. So 1 N downward force needed to hold it.