Question

Water flows along a pipe of radius $0.6cm$ at $8cm$ per second. This pipe is draining the water from a tank which holds $1000$ litres of water when full. How long would it take to completely empty the tank ?

Answer 1

1 litre = 1000 $c{m}^3$

$\therefore$ volume of tank = 1000000 $c{m}^3$

volume of water flowing out of the pipe per second = $\pi r^{2}l$

where $r$ is the radius of the pipe and $l$ is the flow per second

$r=0.6cm$ and $l=8cm/s$

substituting the values we have volume of water flowing out of the pipe per second = $9.0477c{m}^3/s$

$\therefore$ time taken to empty tank = $\frac{volumeoftank}{volumeofflowingoutthroughthepipepersecond}$ $=\frac{1000000}{9.0477}$ $=110525.32seconds$

i.e $30.7$ hours.