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Air as an ideal gas enters a diffuser operating at steady state at 5 bar, 280 K with a velocity of 510 m/s. The exit velocity is

Nataly [62]

Answer:

Explanation:

Calculating the exit temperature for K = 1.4

The value of $c_p$ is determined via the expression:

$c_p = \frac{KR}{K_1}$

where ;

R = universal gas constant = $\frac{8.314 \ J}{28.97 \ kg.K}$

k = constant = 1.4

$c_p = \frac{1.4(\frac{8.314}{28.97} )}{1.4 -1}$

$c_p= 1.004 \ kJ/kg.K$

The derived expression from mass and energy rate balances reduce for the isothermal process of ideal gas is :

$0=(h_1-h_2)+\frac{(v_1^2-v_2^2)}{2}$ ------ equation(1)

we can rewrite the above equation as :

$0 = c_p(T_1-T_2)+ \frac{(v_1^2-v_2^2)}{2}$

$T_2 =T_1+ \frac{(v_1^2-v_2^2)}{2 c_p}$

where:

$T_1 = 280 K \\ \\ v_1 = 510 m/s \\ \\ v_2 = 120 m/s \\ \\c_p = 1.0004 \ kJ/kg.K$

$T_2= 280+\frac{((510)^2-(120)^2)}{2(1.004)} *\frac{1}{10^3}$

$T_2 = 402.36 \ K$

Thus, the exit temperature = 402.36 K

The exit pressure is determined by using the relation: $\frac{T_2}{T_1} = (\frac{P_2}{P_1})^\frac{k}{k-1}$

$P_2=P_1(\frac{T_2}{T_1})^\frac{k}{k-1}$

$P_2 = 5 (\frac{402.36}{280} )^\frac{1.4}{1.4-1}$

$P_2 = 17.79 \ bar$

Therefore, the exit pressure is 17.79 bar

7 0

2 years ago

A fixed electric space heater wired by a cable with an ampacity of 30 A should draw a maximum current of A. 30 A. B. 24 A. C. 15

Nookie1986 [14]

Answer: The correct answer is option (A).

Explanation

Ampacity is defined as the maximum amount of the current carried by the conductor continuously without exceeding its temperature rating.

The ampacity of the wire of the heater is 30 A .And this means that wire is capable of conducting current of maximum amount of 30 Ampere through it without exceeding its temperature rating.

Hence, the correct answer is option is (A).

7 0

3 years ago

A circular bird feeder 19.0 cm in radius has rotational inertia 0.130 kg·m2. It's suspended by a thin wire and is spinning slowl

soldi70 [24.7K]

Answer:

N₂=20.05 rpm

Explanation:

Given that

R= 19 cm

I=0.13 kg.m²

N₁ = 24.2 rpm

$\omega_1=\dfrac{2\pi \times 24.2}{60}\ rda/s$

ω₁= 2.5 rad/s

m= 173 g = 0.173 kg

v=1.2 m

Initial angular momentum L₁

L₁ = Iω₁ - m v r ( negative sign because bird coming opposite to motion of the wire motion)

Final linear momentum L₂

L₂= I₂ ω₂

I₂ = I + m r²

The is no any external torque that is why angular momentum will be conserve

L₁ = L₂

Iω₁ - m v r = I₂ ω₂

Iω₁ - m v r = ( I + m r²) ω₂

Now by putting the all values

Iω₁ - m v r = ( I + m r²) ω₂

0.13 x 2.5 - 0.173 x 1.2 x 0.19 = ( 0.13 + 0.173 x 0.19²) ω₂

0.325 - 0.0394 = 0.136 ω₂

ω₂ = 2.1 rad/s

$\omega_2=\dfrac{2\pi \times N_2}{60}$

N₂=20.05 rpm

3 0

3 years ago

A pendulum is raised to a height of 0.3m above its lowest point and released. What is the velocity of the pendulum at its lowest

enyata [817]

Answer:

v = 2,425 m / s

Explanation:

A simple pendulum has anergy stored at the highest point of the path and this energy is conserved throughout the movement.

highest point

Em₀ = U = m g y

lowest point

$Em_{f}$ = K = ½ m v²

Em₀ = Em_{f}

mg y = ½ m v²

v = √ 2gy

let's calculate

v = √ (2 9.8 0.3)

v = 2,425 m / s

3 0

3 years ago

Alannah added a strip of zinc to a beaker containing a solution of copper

USPshnik [31]

The solution of copper sulfate was too cold

Explanation:

8 0

2 years ago

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