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A shower head has 20 circular openings, each with radius \(1.0 \mathrm{~mm}\). The shower head is connected to a pipe with radius \(0.80 \mathrm{~cm}\). If the speed of water in the pipe is \(3.0 \mathrm{~m} / \mathrm{s},\) what is its speed as it exits the shower-head openings?

Short Answer

Expert verified
The speed of water as it exits the shower-head openings can be calculated by substituting the values discovered in the above steps into the continuity equation.

Step by step solution

01

Determine the Area of the Pipe

To determine the area of the pipe, which is circular, we use the formula \(Area = \pi r^2\), where \(r = 0.80 \mathrm{~cm} = 0.008 \mathrm{~m}\). Converting radius to meters for consistency in units. Hence, \(A_1 = \pi * (0.008)^2 \mathrm{~m^2}\).
02

Determine the Area of Each Opening

Similar to the above step, we calculate the area of each opening using the formula \(Area = \pi r^2\), where \( r = 1.0 \mathrm{~mm} = 0.001 \mathrm{~m}\). Hence, \(Area\_of\_each\_opening = \pi * (0.001)^2 \mathrm{~m^2}\).
03

Determine the Total Area of all Openings

The total area of all openings is simply 20 times the area of each opening. We have 20 openings, hence \(A_2 = 20 * Area\_of\_each\_opening \mathrm{~m^2}\).
04

Substitute Values into Continuity Equation

The continutiy equation is given by \(A_1v_1 = A_2v_2\). We substitute \(A_1, A_2, v_1\) values into this to find \(v_2\) as follows: \( A_1*v_1 = A_2*v_2 \Rightarrow v_2 = \frac{A_1*v_1}{A_2} \mathrm{~m/s}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Continuity Equation
The Continuity Equation is a fundamental principle in fluid dynamics, which states that the mass flow rate must be constant along a streamline. This means that the flow rate of a fluid entering a system must equal the flow rate leaving the system. For incompressible fluids, the equation is given by:
  • \( A_1 v_1 = A_2 v_2 \)
where \( A_1 \) and \( A_2 \) are the cross-sectional areas of the pipe and opening, and \( v_1 \) and \( v_2 \) are the velocities of the fluid at those points.
Applying the Continuity Equation helps in determining the velocity of fluid at different sections of a conduit, such as a pipe connected to a showerhead. Here, it allows us to equate the initial and final flow scenarios, which is crucial when the geometry changes from a larger pipe to multiple smaller openings.
Pipe Flow
Pipe Flow refers to the movement of liquid through a pipe. Often, the fluid flows under pressure, regulated by the pipe's diameter and the liquid's velocity. In our scenario, the pipe supplies water to a shower head. This flow is described in terms of:
  • The flow rate: the volume of fluid passing through a section per unit time.
  • Velocity: the speed at which the fluid moves in a certain direction.
  • Cross-sectional area: the area through which the fluid flows.
Considering the showerhead attached to a pipe, ensuring efficient water delivery, it's necessary to calculate both the area of the entire pipe and individual openings. Understanding pipe flow, especially continuity, is key in designing systems for optimal performance.
Area Calculation
To find how fast water exits the showerhead, we must first calculate the areas of both the pipe and the showerhead openings. This involves the formula for the area of a circle:
  • \( A = \pi r^2 \)
First, calculate the pipe's area:1. Convert the pipe radius from centimeters to meters: \( 0.80 \, \text{cm} = 0.008 \, \text{m} \).2. Plug the radius into the area formula: \( A_1 = \pi (0.008)^2 \).Next, find the showerhead openings' area:1. Convert the opening radius from millimeters to meters: \( 1.0 \, \text{mm} = 0.001 \, \text{m} \).2. Calculate the area for one opening using the same formula.3. Multiply by the number of openings to find the total exit area.
Velocity Calculation
Knowing the areas of the pipe and the openings allows us to calculate the velocity of water as it exits the showerhead. Using the Continuity Equation, we equate the flow conditions:First, we have:
  • Initial Flow: pipe area \( A_1 \), and velocity \( v_1 = 3.0 \, \text{m/s} \)
  • Final Flow: total exit area \( A_2 \), velocity \( v_2 \)
To find \( v_2 \):1. Use the continuity equation: \( A_1 v_1 = A_2 v_2 \).2. Rearrange to solve for \( v_2 \): \( v_2 = \frac{A_1 v_1}{A_2} \).This provides the velocity at which water flows out of the showerhead, considering the constraints posed by the narrower exits compared to the supply pipe.

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Most popular questions from this chapter

A cubical block of wood, \(10.0 \mathrm{~cm}\) on a side, floats at the interface between oil and water with its lower surface \(1.50 \mathrm{~cm}\) below the interface (Fig. E12.33). The density of the oil is \(790 \mathrm{~kg} / \mathrm{m}^{3}\). (a) What is the gauge pressure at the upper face of the block? (b) What is the gauge pressure at the lower face of the block? (c) What are the mass and density of the block?

A cube \(5.0 \mathrm{~cm}\) on each side is made of a metal alloy. After you drill a cylindrical hole \(2.0 \mathrm{~cm}\) in diameter all the way through and perpendicular to one face, you find that the cube weighs \(6.30 \mathrm{~N}\). (a) What is the density of this metal? (b) What did the cube weigh before you drilled the hole in it?

A plastic ball has radius \(12.0 \mathrm{~cm}\) and floats in water with \(24.0 \%\) of its volume submerged. (a) What force must you apply to the ball to hold it at rest totally below the surface of the water? (b) If you let go of the ball, what is its acceleration the instant you release it?

A \(900 \mathrm{~N}\) athlete in very good condition does not float in a fresh- water pool. To keep him from sinking to the bottom, an upward force of \(20 \mathrm{~N}\) must be applied to him. What are his volume and his average density?

On the afternoon of January \(15,1919,\) an unusually warm day in Boston, a 17.7 -m-high, 27.4-m-diameter cylindrical metal tank used for storing molasses ruptured. Molasses flooded into the streets in a 5-m-deep stream, killing pedestrians and horses and knocking down buildings. The molasses had a density of \(1600 \mathrm{~kg} / \mathrm{m}^{3}\). If the tank was full before the accident, what was the total outward force the molasses exerted on its sides? (Hint: Consider the outward force on a circular ring of the tank wall of width \(d y\) and at a depth \(y\) below the surface. Integrate to find the total outward force. Assume that before the tank ruptured, the pressure at the surface of the molasses was equal to the air pressure outside the tank.)

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