Couple of pretty simple liquid q's

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Homework Help Overview

The discussion revolves around fluid dynamics, specifically the relationship between the velocity of a liquid projected from a tank and the height it reaches. The original poster presents a problem involving a cylindrical tank filled with water and the effects of gravity on the water exiting through an orifice.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between the initial velocity of water exiting the tank and the height it reaches. Questions arise regarding the initial speed of the water when it exits and the application of Bernoulli's equation to determine the exit velocity. There is also discussion about the correct interpretation of variables in the equation.

Discussion Status

Some participants have offered guidance on using Bernoulli's equation to find the initial speed of the water. Others are questioning the assumptions regarding the heights used in the calculations and whether the initial conditions have been correctly interpreted. Multiple interpretations of the problem setup are being explored.

Contextual Notes

Participants are considering the effects of gravity and the specific dimensions of the tank and orifice. There is uncertainty about the correct values for height in the context of the problem, which may affect the calculations.

Jacob87411
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1) First ones just I am curious about what's the relationship between the velocity of a liquid being projected, like out of a hose, vertically and the height it goes.

2) An actual problem: A cylindrical tank .9 m in radius rests atop a platform 6 m high. Initially the tank is filled with water to a depth of h=3m. A plug whose area is 6.3 cm^2 is removed from an orifice in the side of the tank at the bottom. What is the speed of the stream as it strikes the ground.

Will the water have an initially speed when it comes out? Obviously gravity is what is going to accelerate it down at 9.8 m/s, I thought that it would just be the acceleration multiplied by the time because it wouldn't have an initial speed, it was just coming out. This seems to simple and doesn't use the informatyion they gave me so guessing its not the answer
 
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Jacob87411 said:
1) First ones just I am curious about what's the relationship between the velocity of a liquid being projected, like out of a hose, vertically and the height it goes.

2) An actual problem: A cylindrical tank .9 m in radius rests atop a platform 6 m high. Initially the tank is filled with water to a depth of h=3m. A plug whose area is 6.3 cm^2 is removed from an orifice in the side of the tank at the bottom. What is the speed of the stream as it strikes the ground.

Will the water have an initially speed when it comes out? Obviously gravity is what is going to accelerate it down at 9.8 m/s, I thought that it would just be the acceleration multiplied by the time because it wouldn't have an initial speed, it was just coming out. This seems to simple and doesn't use the informatyion they gave me so guessing its not the answer

It isn't simple.It's not too difficult,either...Well,...to me,that is...
Calculate the speed at which the particles (molecules if u prefer) at the surface of the water inside the tank begin to fall,once u've opened the plug.Use Bernoulli's equation of continuity for incompressible fluids (the one that states that the flow is conservative),to find at what speed the particles of water exit the tank through the hole.
That would be your initial speed of the water that comes out of the tank.Plug it in the equation for motion in the gravitational field to find the final speed (the speed at the contact with the ground).

Daniel.
 
P1 + 1/2PV^2 + PGY1 = P2 + 1/2PV2^2 + PGY2

(I know the P's in 1/2PV^2 are rho for density, new here with the greek letters)

P1 and P2 both 1 atm?
Y1 = The top of the barrel so 3m since its filled up 3m?
Y2 = 0?

If that is the correct way I should be all set
 
Or should Y1 be 9 and Y2 be 3 since the barrel is 6m above the ground
 

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