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3 years ago

Which of these physical concepts is most important in civil engineering?

Engineering

1 answer:

mezya [45]3 years ago

3 0

Answer:

Option A (energy transformations) is the correct solution.

Explanation:

Energy has become a local matter that has been primarily described as the commitment to deal as well as to generate heat. There are several other power sources, which can either be transferred or transformed to several other renewable technologies.
This same fundamental law defined that the energy required including its universe has been corrected and therefore that energy is being generated as well as severely damaged but should only be moved from one location to the next.

Those certain possibilities are not connected to the circumstance in question. And therefore this answer seems to be the correct one.

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Travel Planning or Destination Planning will help make your travel more efficient, and not necessary a risk reduction plan as yo

galben [10]

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True

3 0

2 years ago

Read 2 more answers

A 220-V electric heater has two heating coils that can be switched such that either coil can be used independently or the two ca

Nana76 [90]

Answer:

The resistances of both coils are 131.7 Ω and 29.64 Ω.

Explanation:

Since, there are two coils, they can be used independently or in series or parallel. The power is given as:

Power = P = VI

but, from Ohm's Law:

V = IR

I = V/R

therefore,

P = V²/R

R = V²/P

Hence, the resistance (R) and (P) are inversely proportional. Therefore, the maximum value of resistance will give minimum power, that is, 300 W. And the maximum resistance will be in series arrangement, as in series the total resistance gets higher than, any individual resistance.

Therefore,

Rmax = V²/Pmin = R1 + R2

R1 + R2 = (220 V)²/300 W

R1 + R2 = 161.333 Ω ______ en (1)

Similarly, the minimum resistance will give maximum power. And the minimum resistance will occur in parallel combination. Because equivalent resistance of parallel combination is less than any individual resistance.

Therefore,

(R1 R2)/(R1 + R2) = (220 V)²/2000 W

using eqn (1), we get:

(R1 R2) / 161.333 Ω = 24.2 Ω

R1 R2 = 3904.266 Ω²

R1 = 3904.266 Ω²/R2 _____ eqn (2)

Using this value of R1 in eqn (1), we get:

3904.266/R2 +R2 = 161.333

(R2)² - 161.333 R2 +3904.266 = 0

Solving this quadratic eqn we get two values of R2 as:

R2 = 131.7 Ω OR R2 = 29.64 Ω

when ,we substitute these values in eqn (1) to find R1, we get get the same two values as R2, alternatively. This means that the two coils have these resistance, and the order does not matter.

<u>Therefore, the resistance of both coils are found to be 131.7 Ω and 29.64 Ω</u>

7 0

3 years ago

Determine the maximum height (in inches) that a lift pump can raise water (0.9971 g/ml) from a well at normal atmospheric pressu

solniwko [45]

Answer:Height = 30 inches

Mass of water / Volume of water x Gravity constant for Earth x Density of Water. This cancels out to give us mass/volume, which is then cancelling mass, giving us the final unit of length/area (in this case inches).

Explanation:

Height = 30 inches.

Units cancelled:

30/30 x 9.8 x 0.9971 = 30/39.97

The final units are in inches!

2. Determine the weight (in pounds) that an ice cube at 32°F will displace when placed in water at 75°F.

Weight of ice cube / Volume of water x Gravity constant for Earth x Density of Ice = Weight displaced by ice cube in pounds

Weight of ice cube / Volume of water x Gravity constant for Earth x Density of Ice = 0.5/75 x 32 x 0.92 = 0.5/22.67

The final units are in pounds!

3. Determine the mass (in grams) of an ice cube at 32°F when placed in water at 75°F (assume no change in volume).

Mass of Ice Cube / Volume of Water x Gravity constant for Earth x Density of Ice = Mass of ice cube in grams

Mass of Ice Cube / Volume of Water x Gravity constant for Earth x Density of Ice = 0.5/75 x 32 x 0.92 = 15/22.67

The final units are in grams!

7 0

3 years ago

The components of an electronic system dissipating 180 W are located in a 1-m-long horizontal duct whose cross section is 16 cm

oee [108]

Answer:

a) The exit temperature is 39.25°C

b) The highest component surface is 132.22°C

c) The average temperature for air equal to 35°C is a good assumption because the air temperature at the inlet will increase due to the result in the heat gain produced by the duct and whose surface is exposed to a flow of hot.

Explanation:

a) The properties of the air at 35°C:

p = density = 1.145 kg/m³

v = 1.655x10⁻⁵m²/s

k = 0.02625 W/m°C

Pr = 0.7268

cp = 1007 J/kg°C

a) The mass flow rate of air is equal to:

$m=\rho *V = 1.145*0.65=0.7443kg/min=0.0124kg/s$

The exit temperature is:

$T=T_{i} +\frac{Q}{m*c_{p} } =27+\frac{0.85*180}{0.0124*1007} =39.25$ °C

b) The mean fluid velocity is:

$V_{m} =\frac{V}{A} =\frac{0.65}{0.16*0.16} =25.4m/min=0.4232m/s$

The hydraulic diameter is:

$D_{h} =\frac{4A}{p} =\frac{4*0.16*0.16}{4*0.16} =0.16m$

The Reynold´s number is:

$Re=\frac{VD_{h} }{v} =\frac{0.4232*0.16}{1.655x10^{-5} } =4091.36$

Assuming fully developed turbulent flow, the Nusselt number is:

$Nu=0.023Re^{0.8} *Pr^{0.4} =0.023*4091.36^{0.8} *0.7268^{0.4} =15.69$

$h=\frac{k*Nu}{D_{h} } =\frac{0.02625*15.69}{0.16} =2.57W/m^{2} C$

The highest component surface temperature is:

$T=T_{e} +\frac{\frac{Q}{A} }{h} =39.2+\frac{0.85*\frac{180}{4*0.16*1} }{2.57} =132.22$ °C

6 0

4 years ago

What is an isentropic process?

snow_tiger [21]

Answer: Isentropic process is the process in fluids which have a constant entropy.

Explanation: The isentropic process is considered as the ideal thermodynamical process and has both adiabatic as well as reversible processes in internal form.This process supports no transfer of heat and no transformation of matter .The entropy of the provided mass also remains unchanged or consistent.These processes are usually carried out on material on the efficient device.

5 0

3 years ago