Question

A rectangular water-tank measuring 80 cm x 60 cm is filled form a pipe of cross-sectional area 1.5 cm², the water emerging at 3.2 m/s. How long does it take to fill the tank?

Answer 1

Vol. of the rectangular tank = 80 x 60 x 60 cm³ = 288000 cm³

One liter = 1000 cm³

Vol. of water flowing in per sec =
`1.5"cm"^2 xx 3.2"m"/s = 1.5"cm"^2 xx ((3.2 xx 100)"cm")/"s"`

                                     = `480 "cm"^3/"s"`

Vol. of water flowing in 1 min= 480 x 60 = 28800cm³ 

Hence,

28800 cm³  can be filled = 1 min

288000cm³ can be filled =`( 1/28800 xx 288000) min=10min`