All categories

3 years ago

Why can the human powered generator be the worst option for the rescue team

Engineering

1 answer:

zimovet [89]3 years ago

4 0

Answer:

Human powered generators are the best energy source for the rescue team as it doesn't require any lengthy time consuming resource but only the power of single human being. Just like fossil fuels, the human power is a kind of renewable energy source that does no harm to the environment and can be used whenever required.

Explanation:

You might be interested in

A rectangular block of material with shear modulus G= 620 MPa is fixed to rigid plates at its top and bottom surfaces. Thelower

PIT_PIT [208]

Answer:

γ $_{xy}$ =0.01, P=248 kN

Explanation:

Given Data:

displacement = 2mm ;

height = 200mm ;

l = 400mm ;

w = 100 ;

G = 620 MPa = 620 N//mm²; 1MPa = 1N//mm²

a. Average Shear Strain:

The average shear strain can be determined by dividing the total displacement of plate by height

γ $_{xy}$ = displacement / total height

= 2/200 = 0.01

b. Force P on upper plate:

Now, as we know that force per unit area equals to stress

τ = P/A

Also, τ = Gγ $_{xy}$

By comapring both equations, we get

P/A = Gγ $_{xy}$ ------------ eq(1)

First we need to calculate total area,

A = l*w = 400 * 100= 4*10^4mm²

By putting the values in equation 1, we get

P/40000 = 620 * 0.01

P = 248000 N or 2.48 *10^5 N or 248 kN

6 0

3 years ago

Convection ovens operate on the principle of inducing forced convection inside the oven chamber with a fan. A small cake is to b

coldgirl [10]

Answer:

A) q'_free = 3146.41 W/m²

B) q'_forced = 7521.41 W/m²

Explanation:

We are given;

Free convection coefficient; h_fr = 5 W/m²K

Force convection coefficient; h_forced = 30 W/m²K

Emissivity; ε = 0.95

Temperature of surrounding which is equal to temperature of air; T_s = T_air = 200°C = 473K

Initial temperature; T_i = 25°C = 298K

A) Now, since the convection feature is disabled, the mode of heat transfer associated with this condition is through free convection and radiation.

Thus, the formula for the heat flux under this condition is given as;

q'_free = q'_free convection + q'_radiation

q'_free convection = h_free(T_∞ - T_i) where T_∞ is equivalent to the value of T_air

Also, q'_radiation = ε•σ((T_air)⁴ - (T_i)⁴)

Where, σ is stephan boltzmann constant and has a constant value of 5.67 × 10^(−8) W/m²K⁴

Thus, rewriting;

q'_free = q'_free convection + q'_radiation

We have;

q'_free = [h_free(T_∞ - T_i)] + [ε•σ((T_air)⁴ - (T_i)⁴)]

Plugging in the relevant values to obtain;

q'_free = [5(473 - 298)] + [0.95•5.67 × 10^(−8)((473)⁴ - (298)⁴)]

q'_free = 875 + 2271.41

q'_free = 3146.41 W/m²

B) Now, in this case, since the convection feature is disabled, the mode of heat transfer associated with this condition is through forced convection and radiation.

Thus, the formula for the heat flux under this condition is given as;

q'_forced = q'_forced convection + q'_radiation

Where;

q'_forced convection = h_forced(T_∞ - T_i) where T_∞ is equivalent to the value of T_air

Also, q'_radiation = ε•σ((T_air)⁴ - (T_i)⁴)

Thus, rewriting;

q'_forced = q'_free convection + q'_radiation

We have;

q'_forced = [h_forced(T_∞ - T_i)] + [ε•σ((T_air)⁴ - (T_i)⁴)]

Plugging in the relevant values to obtain;

q'_forced = [30(473 - 298)] + [0.95•5.67 × 10^(−8)((473)⁴ - (298)⁴)]

q'_forced = 5250 + 2271.41

q'_forced = 7521.41 W/m²

7 0

4 years ago

The acceleration due to gravity at sea level is g=9.81 m/s^2. The radius of the earth is 6370 km. The universal gravitational co

solmaris [256]

Answer:

Mass of earth will be $M=5.96\times 10^{24}kg$

Explanation:

We have given acceleration due to gravity $g=9.81m/sec^2$

Radius of earth = 6370 km = $6370\times 10^3m$

Gravitational constant $G=6.67\times 10^{-11}Nm^2/kg^2$

We know that acceleration due to gravity is given by

$g=\frac{GM}{R^2}$ , here G is gravitational constant, M is mass of earth and R is radius of earth

So $9.81=\frac{6.67\times 10^{-11}\times M}{(6370\times 10^3)^2}$

$M=5.96\times 10^{24}kg$

So mass of earth will be $M=5.96\times 10^{24}kg$

3 0

3 years ago

Pie charts should have no more than eight segments. True or False?

Pepsi [2]

Answer:

Explanation:

Pie charts generally should have no more than eight segments.

6 0

3 years ago

Read 2 more answers

You are an engineer in an electric-generation station. You know that the flames in the boiler reach a temperature of 1200 K and

olga nikolaevna [1]

Answer:

The maximum efficiency the plant will ever achieve is 75%

Explanation:

From the question given, we recall the following:

Th flames in the boiler reaches a temperature of = 1200K

the cooling water is = 300K

The maximum efficiency the plant will achieve is defined as:

Let nmax = 1 - Tmin /Tmax

Where,

Tmin = Minimum Temperature in plants

Tmax = Maximum Temperature in plants

The temperature of the cooling water = Tmin = 300K

The temperature of the flames in boiler = Tmax = 1200k=K

The maximum efficiency becomes:

nmax = 1 - Tmin /Tmax

nmax = 1 - 300 /1200

nmax = 1-1/4 =0.75

nmax = 75%

5 0

4 years ago