Question

why did we not just use Qin = Q our and solve

where did the other variables came in the equation

i thought convesation of mass is Min - Mout

https://www.chegg.com/homework-help/fundamentals-of-fluid-mechanics-7th-edition-chapter-5-problem-12p-solution-9781118116135?trackid=0530221cc62f&strackid=a5d176cfc25c

Answer 1

Because in this mass of inside gasoline is also changing with time and due to this volume of water is also changing with time that's why we did not simply write the mass conversion equation Qin= Q out, ( It can be written as Qin= Q out if there is no change in mass of gasoline and volume of water with respect to time, Initially cylinder is not filled completely( from figure we can say this).

Here also Change in mass = Q*Y

in this question Q(flow rate and unit weight of water are different for both so it can not cancelled out from equation.

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