A cylindrical tube is fitted coaxially at one of its ends into a hole made at the centre of a large disc. The structure is held firmly at a height h above a horizontal floor, keeping plane of the disc horizontal. When an incompressible non-viscous fluid of density ρ is fed at a constant rate μ (kg/s) into the tube completely filling the tube, the fluid spreads evenly in all directions in the gap between the disc and the floor. Find radius r of the fluid spreading in the gap as a function of time t.