A small steam whistle (perfectly insulated and doing no

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A small steam whistle (perfectly insulated and doing no shaft work) causes a drop of 0.8 kJ/kg in enthalpy of steam from entry to exit. If the kinetic energy of the steam at entry is negligible, the velocity of the steam at exit is

1. 4 m/s
2. 40 m/s
3. 80 m/s
4. 120 m/s

Correct Option: B

v²₁	+ h₁ =	v²₂
2	+ h₁ =	2

Heres v₁ = 0, therefore

h₁ =	v²₂	+ h₂
	2

or v₂ = √2(h₁ - h₂) = √2 × 0.8 × 1000 = 40 m/sec.