Question

On a windy day, the wind blows at 18 mph as it enters the south side of a Pay Tunnel (25'W x 16'6"H x 4380'L). Using the Conservation of Momentum equation, what is the speed of the wind as it exits on the north side of the same tunnel?

Answer 1

As directions (south and north) are opposite to each other, hence from the reference to co ordinate sysytem it is a one dimentional flow.

And as no clue is given time dependence of flow rate hence no storage of mass is seen. The system is assumed to be steady.

m_s.v_s=m_n.v_n

_and   m_s=​​​​m_n=m

so we have v_s=v_n=18 mph

where m is mass flow rate

and v is velocity

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