An object floats in a fluid when it displaces it's

Analyze the question: The question is about the law of flotation, which comes from Archimedes' principle. It asks what an object must displace in order to float.

Concept:

• Archimedes' principle says that when a body is wholly or partly immersed in a fluid, it experiences an upthrust equal to the weight of the fluid it displaces.
• The law of flotation says that a floating body displaces its own weight of the fluid in which it floats.

Step-by-step solution:

1. For an object to float, it must be in equilibrium. The upthrust upward must balance the weight of the object downward.
2. Upthrust = weight of fluid displaced.
3. So at equilibrium: weight of object = weight of fluid displaced.
4. Now check each option: • A. Volume of liquid: Wrong. The volume displaced equals the volume of the submerged part only, not the whole object. This volume does not by itself tell you whether the object floats. • B. Mass of fluid: Mass is related to weight (W = mg), so it is numerically close. But the standard statement of the law of flotation uses weight, because upthrust is a force. • C. Weight of fluid: Correct. The weight of fluid displaced equals the weight of the floating object, which is the law of flotation. • D. Density of fluid: Wrong. Density is a property of the fluid, and it is not something an object displaces.

Answer: The object floats when it displaces its own weight of the fluid in which it floats, which is option C.

Exam tip: Remember "upthrust is a force, so it equals a weight." When you see "floats," think "weight of object = weight of fluid displaced." Watch out for the mass option, since WAEC usually phrases Archimedes' principle in terms of weight.