Which of the following is a job title for a worker in the design and pre-construction phase of a construction project?

An object whose mass is 251 kg is located at an elevation of 24 m above the surface of the earth. For g-9.78 ms, determine the g

Harlamova29_29 [7]

Answer:

Gravitational Potential =58.914 KJ

Explanation:

We know that

$Gravitational Potential Energy = mass\times g\times Height$

Given mass = 251 kg

Height= 24 m

g is acceleration due to gravity = $9.78m/s^{2}$

Applying values in the equation we get

$Gravitational Potential Energy=251X9.78X24 Joules$

$Gravitational Potential Energy=58914.72 Joules$

$Gravitational Potential Energy =\frac{58914.72}{1000}KJ= 58.914KJ$

4 0

4 years ago

Re armature of a 4 pole DC generator is required to generate an emf of 520v on open circuit when revolving at a speed of 660rpm.

bija089 [108]

Since the armature is wave wound, the magnetic flux per pole is 0.0274 Weber.

Given the following data:

Emf = 520 Volts

Speed = 660 r.p.m

Number of armature conductors = 144 slots

Number of poles = 4 poles

Number of parallel paths = 2

To find the magnetic flux per pole:

Mathematically, the emf generated by a DC generator is given by the formula;

$E = \frac{\theta ZN}{60}$ × $\frac{P}{A}$

Where:

E is the electromotive force in the DC generator.

Z is the total number of armature conductors.

N is the speed or armature rotation in r.p.m.

P is the number of poles.

A is the number of parallel paths in armature.

Ф is the magnetic flux.

First of all, we would determine the total number of armature conductors:

$Z = 144$ × $2$ × $3$

Z = 864

Substituting the given parameters into the formula, we have;

$520 = \frac{\theta (864)(660)}{60}$ × $\frac{4}{2}$

$520 = \theta (864)(11)$ × $2$

$520 = 19008 \theta \\\\\Theta = \frac{520}{19008}$

Magnetic flux = 0.0274 Weber.

Therefore, the magnetic flux per pole is 0.0274 Weber.

5 0

3 years ago

Which of the following is NOT true concerning the color of minerals? A. Some minerals have a consistent color, but many have a r

mixer [17]

Answer:

Option D

A mineral’s color reflects the wavelengths of light that are absorbed by the mineral.

Explanation:

Color is one of the physical properties of minerals. Many minerals have a wide range of colors but there are some minerals with one consistent color and such minerals are referred as monochromatic minerals for example azurite. Normally, the streak color tends to be less variable than the color of the whole mineral and impurities or minor chemical components in a mineral react and often control the display color of resultant mineral. Option D is incorrect since mineral's color don't reflect wavelengths of light absorbed by such minerals.

5 0

3 years ago

[4 points] Does the green LED emit light when you connect the banana plug wires across it? What does that say about the threshol

castortr0y [4]

Yes, the green LED emits light when we connect the banana plug wires across it.

This indicates that the threshold voltage is lower for the green LED light than the blue.

Explanation:

A banana plug is named for its resemblance to the shape of a banana. They are wider in the middle of the plug, and narrower at the top and bottom. The banana plug can be easily plugged or unplugged into the ports of speaker or receiver.

LED lights emit photons when it is applied with electrical charge. LED lights are more efficient and last longer than incandescent light bulbs. Green light is commonly provides the calming effect. It is generally used in hyper-pigmentation treatment.

4 0

3 years ago

An escalator handles a steady load of 26 people per minute in elevating them from the first to the second floor through a vertic

photoshop1234 [79]

Answer:

$\eta = 70.711\,\%$

Explanation:

The power needed to make the escalator working is obtained by means of the Work-Energy Theorem:

$\dot W = \dot U_{g}$

$\dot W = \dot n \cdot m_{p}\cdot g \cdot \Delta y$

$\dot W = \left(26\,\frac{persons}{min}\right)\cdot (124\,lbm)\cdot \left(32.174\,\frac{ft}{s^{2}}\right)\cdot \left(\frac{1\,lbf}{32.174\,\frac{lbm\cdot ft}{s^{2}} } \right)\cdot (27.5\,ft)$

$\dot W = 88660\,\frac{lbf\cdot ft}{min}\,\left(2.687\,hp\right)$

The mechanical efficiency of the escalator is:

$\eta = \frac{2.687\,hp}{3.8\,hp}\times 100\,\%$

$\eta = 70.711\,\%$

3 0

3 years ago