d) Upthrust

c) p = hρg; upthrust on an object in a fluid; Archimedes’ principle

upthrust = the upwards force exerted by a fluid on an object against the direction of its weight

U = Vρg

• upthrust (N) = volume of the submerged part of an object (m³) × density of the fluid (kgm^-3) × acceleration of free fall (ms^-2)

Archimedes’ principle → (whether or not the object is in equilibrium) upthrust exerted by a fluid on a submerged object = weight of the fluid displaced by the submerged object

volume of the submerged part of an object = volume of the displaced fluid

weight of a floating object = weight of the displaced fluid