The Student Room Group

A level physics

Is upthrust due to Newton's third law? An object submerged fully in water exerts a force on the fluid. The fluid exerts an equal and opposite force on the object,which is equal to the weight of the displaced fluid.Am I correct?Please do rectify my mistakes if I made any
Reply 1
Although what you have said is true, it doesn't really explain the origin of the upthrust (i.e. why the fluid exerts a force which is equal to to the weight of displaced fluid). In order to show that, consider the difference of forces acting the top and bottom surfaces of object, and use the fact that pressue in fluid p=ρghp = \rho g h.

Quick Reply

Latest