Acircular conical reservoir has depth 20 feet and radius of the top 10 feet. water is leaking out so that the surface is falling at the rate of 1 2 ft hr .the rate, in cubic feet per hour, at which the water is leaving the reservoir when the water is 8 feet deep is

As per given condition we know that vertex angle of the cone is given as

so here we can say that vertex angle will remain constant

so here

now for the volume we can say

also we can say

so here we will have

now for volume flow rate

now plug in all data

this is poiselle's equation from fluid mechanic in physics. mech eng

increase masses, decrease separation