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stiks02 [169]
3 years ago
13

A fireboat is to fight fires at coastal areas by drawing seawater with a density of 1030 kg/m through a 20-cm-diameter pipe at a

rate of 0.1 m /s and discharging it through a hose nozzle with an exit diameter of 5 cm. The total irreversible head loss of the system is 3 m, and the position of the nozzle is 3 m above sea level. For a pump efficiency of 70 percent, determine the required shaft power input to the pump and the water discharge velocity.
Engineering
1 answer:
stealth61 [152]3 years ago
3 0

Answer:

A. 50.93 m/s

B. 201 kW

Explanation:

We have that pump is moving 0.1m³ of water every second. The nozzle is 5cm diameter = 0.05m , or 2.5cm radius. 2.5cm = 0.025m. The cross sectional area of the nozzle is therefore, A = πr²

π×0.025²

= 0.001963m²

Therefore, for 0.1m³ of water to pass through this nozzle in 1 second, it must be travelling at

0.1 / 0.001963

= 50.93 m/s

Pump is meant to impart energy to the water to raise it 4m from sea level to the nozzle and accelerate it from zero to 50.93m/s through the nozzle. Now, assuming no losses, the dynamic energy of the water is equal to the potential energy it would have if it was stationary at some height h.

P.E = k.E

mgh = 0.5mv²

h = v² / 2g

h = 50.93² / (2 ×9.81)

h = 132.21m

So the equivalent head of water required due to accelerating the water is 132.21m. The static head is 4m since the nozzle is 4m above the sea and there is a further loss of 3m of head in the system due to friction etc. So the total head the pump must provide is

132.21 + 4 + 3

= 139.21m

Density = mass / volume so mass = density × volume.

The Pump is moving 0.1m³ per second of water. Therefore in one second the mass of water pumped is

0.1 × 1030 = 103kg

The total energy transferred from the pump to the water is therefore

Potential enegry, which is = mgh

= 103 ×9.81 × 139.21

= 140,662.0 Nm/s

= 140,662.0 Watts

But, we are told that the pump is only 70% efficient. Which implies

140,662 = 0.7P where P is the power supplied to the pump

so P = 140,662 / 0.7

= 200,946 Watts

= 201 kW

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A controller on an electronic arcade game consists of a variable resistor connected across the plates of a 0.227 μF capacitor. T
anyanavicka [17]

Answer:

R min = 28.173 ohm

R max = 1.55 × 10^{4}  ohm

Explanation:

given data

capacitor = 0.227 μF

charged to 5.03 V

potential difference across the plates =  0.833 V

handled effectively = 11.5 μs to 6.33 ms

solution

we know that resistance range of the resistor is express as

V(t) = V_o \times e^{t\RC}    ...........1

so R will be

R = \frac{t}{C\times ln(\frac{V_o}{V})}    ....................2

put here value

so for t min 11.5 μs

R = \frac{11.5}{0.227\times ln(\frac{5.03}{0.833})}

R min = 28.173 ohm

and

for t max 6.33 ms

R max = \frac{6.33}{11.5} \times 28.173  

R max = 1.55 × 10^{4}  ohm

4 0
3 years ago
Calculate the load, PP, that would cause AA to be displaced 0.01 inches to the right. The wires ABAB and ACAC are A36 steel and
Nataly [62]

Answer:

P = 4.745 kips

Explanation:

Given

ΔL = 0.01 in

E = 29000 KSI

D = 1/2 in  

LAB = LAC = L = 12 in

We get the area as follows

A = π*D²/4 = π*(1/2 in)²/4 = (π/16) in²

Then we use the formula

ΔL = P*L/(A*E)

For AB:

ΔL(AB) = PAB*L/(A*E) = PAB*12 in/((π/16) in²*29*10⁶ PSI)

⇒  ΔL(AB) = (2.107*10⁻⁶ in/lbf)*PAB

For AC:

ΔL(AC) = PAC*L/(A*E) = PAC*12 in/((π/16) in²*29*10⁶ PSI)

⇒  ΔL(AC) = (2.107*10⁻⁶ in/lbf)*PAC

Now, we use the condition

ΔL = ΔL(AB)ₓ + ΔL(AC)ₓ = ΔL(AB)*Cos 30° + ΔL(AC)*Cos 30° = 0.01 in

⇒  ΔL = (2.107*10⁻⁶ in/lbf)*PAB*Cos 30°+(2.107*10⁻⁶ in/lbf)*PAC*Cos 30°= 0.01 in

Knowing that   PAB*Cos 30°+PAC*Cos 30° = P

we have

(2.107*10⁻⁶ in/lbf)*P = 0.01 in

⇒  P = 4745.11 lb = 4.745 kips

The pic shown can help to understand the question.

5 0
4 years ago
A ____ is marked by two sets of double yellow lines, with each set having a broken line on the inside, and a solid line on the o
Vitek1552 [10]

Answer:

  center left-turn lane

Explanation:

A <em>center left turn lane</em> will be marked as described. The arrows, if present, generally indicate that left turns are permitted from the lane with these markings.

__

If the double yellow lines are solid, they are considered to be a "barrier" and are not to be crossed.

7 0
3 years ago
Read 2 more answers
2) The switch in the circuit below has been closed a long time. At t=0, it is opened.
saul85 [17]

Answer:

  il(t) = e^(-100t)

Explanation:

The current from the source when the switch is closed is the current through an equivalent load of 15 + 50║50 = 15+25 = 40 ohms. That is, it is 80/40 = 2 amperes. That current is split evenly between the two parallel 50-ohm resistors, so the initial inductor current is 2/2 = 1 ampere.

The time constant is L/R = 0.20/20 = 0.01 seconds. Then the decaying current is described by ...

  il(t) = e^(-t/.01)

  il(t) = e^(-100t) . . . amperes

8 0
3 years ago
Plz solve the problem
julsineya [31]
I attached a photo that explains and gives the answer to your questions. Had to add a border because the whole picture didn’t fit.

6 0
3 years ago
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