Question

(a) What are fluids? Name two common fluids.
(b) State Archimedes' principle.
(c) When does an object float or sink when placed on the surface of a liquid?

Answer 1

(a) A substance which can flow is called fluid. The common fluids are juice, water, and soup.
(b) Archimedes’ principle states that “when a body is immersed partially or completely in a fluid (liquid or gas), it experiences an upthrust or buoyant force that is equal to the weight of the fluid displaced by body.”
(c) When an object is placed on the surface of water, two forces act on the object:
(i) The gravitational force that act in the downward direction.
(ii) The upthrust or the buoyant force that act in the upward direction.
An object floats on the surface of water if the upthrust of water on the object is greater than the weight of the object. An object sinks if the weight of the object is greater than the upthrust of water on the object.