Water jet from air pressure: find velocity

AI Thread Summary
To determine the gauge air pressure needed for water to exit a fire extinguisher at 30.0 m/s, one must consider the energy dynamics involved. The kinetic energy of the water jet must be calculated, alongside the potential energy required to lift the water 0.500 m. The relationship between these energy forms and the pressure exerted by the air in the tank is crucial. Understanding how these energies interact will lead to the appropriate equations for solving the problem. A solid grasp of the underlying physics principles is essential for finding the solution.
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Homework Statement


it told: 1. Water is forced out of a fire extinguisher by air pressure
2. the water level in the tank is 0.500 m. below the nozzle
3. find gauge air pressure in the tank (above atmosphere) for water jet to have speed of 30.0 m/s

Homework Equations


i don't know what equation i need to use ...!
it ask: How much gauge air pressure in the tank (above atmosphere) for the water jet to have speed of 30.0 m/s

The Attempt at a Solution


I don't know how to do it ... it give me only
gauge air pressure in the tank (above atmosphere)
 
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You really need to have at least SOME thoughts on the physics before anyone can help. I'll give you some starting points, i) how much energy in a mass traveling at 30 m/sec? ii) how much energy to raise a mass 0.5m? iii) how much energy does a mass gain coming out of the high pressure environment inside the bottle (perhaps another property of the body is more important than the mass)? How are these three energies related? Surely you can come up with some formulas that are relevant.
 
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