A submerged object experiences a buoyant force equal to the weight of the displaced water. If the object's volume is 0.002 m^3, the water density is 1000 kg/m^3, and g = 9.8 m/s^2, what is the buoyant force?

A submerged object experiences a buoyant force equal to the weight of the displaced water. If the object's volume is 0.002 m^3, the water density is 1000 kg/m^3, and g = 9.8 m/s^2, what is the buoyant force?

• A. 19.6 N
• B. 9.8 N
• C. 39.2 N
• D. 4.9 N

Answer: (A)

Buoyant force comes from Archimedes’ principle: it equals the weight of the fluid the object displaces. Since the object is fully submerged, it displaces a volume of water equal to its own, 0.002 m^3. The displaced water has mass m = rho * V = 1000 kg/m^3 × 0.002 m^3 = 2 kg. Its weight is m g = 2 kg × 9.8 m/s^2 = 19.6 N. Therefore the buoyant force is 19.6 N. The other numbers would require different volume, density, or gravity (for example, 9.8 N would need 0.001 m^3 of water, or less density), but with the given values, 19.6 N is correct.

Buoyant force comes from Archimedes’ principle: it equals the weight of the fluid the object displaces. Since the object is fully submerged, it displaces a volume of water equal to its own, 0.002 m^3. The displaced water has mass m = rho * V = 1000 kg/m^3 × 0.002 m^3 = 2 kg. Its weight is m g = 2 kg × 9.8 m/s^2 = 19.6 N. Therefore the buoyant force is 19.6 N. The other numbers would require different volume, density, or gravity (for example, 9.8 N would need 0.001 m^3 of water, or less density), but with the given values, 19.6 N is correct.