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4 years ago

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In large gas-turbine power plants, air is preheated by the exhaust gases in a heat exchanger called the regenerator before it en

ters the combustion chamber. Air enters the regenerator at 1 MPa and 550 K at a mass flow rate of 800 kg/min. Heat is transferred to the air at a rate of 3200 kJ/s. Exhaust gases enter the regenerator at 140 kPa and 800 K and leave at 130 kPa and 600 K. Treating the exhaust gases as air, determine (a) the exit temperature of the air and (b) the mass flow rate of exhaust gases. (

1 answer:

alexandr402 [8]4 years ago

7 0

exit temperature of air is 776.128k

the mass flow rate of exhaust gases is 14.89kg/s

Explanation: plz brainly me

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2 skaters with the same mass face eachother standing still, both skaters push off of the other and they move in the opposite dir

likoan [24]

D.) All of these statements are true

Explanation:

We can answer this question by using the law of conservation of momentum.

In fact, for an isolated system (=no external forces acting on it), the total momentum of the system must be conserved.

If we apply this law to this situation, we can say that the total momentum of the 2 skaters before pushing off must be equal to the total momentum of the 2 skaters after pushing off.

Before pushing off, the total momentum of the 2 skaters is zero:

$p_i =0$

Because they are both still, so the total momentum is

$p_i = m_1 u_1 + m_2 u_2 = 0$

Since $u_1 = u_2 = 0$ (where $u_1, u_2$ are the initial velocities of the 2 skaters, while $m_1,m_2$ are their masses)

So, the statement

A.) They have zero momentum before pushing off

is true.

So, according to the law of conservation of momentum, the final momentum must be equal to the initial total momentum:

$p_f = p_i$

And so

$p_f = 0$

Therefore, the statement

B.) The total momentum is 0 after pushing off

is also true.

Finally, the total final momentum can be written as

$p_f = p_1 + p_2$

where

$p_1$ is the momentum of the first skater after pushing off

$p_2$ is the momentum of the second skater after pushing off

Since $p_f = 0$ , this implies that

$p_1+p_2 = 0\\p_2 = -p_1$

So, the statement

C.) They have equal and opposite momenta

is also true.

Therefore the correct option is

D.) All of these statements are true

Learn more about momentum:

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3 years ago

Which describes radioactive decay of a substance?

stepladder [879]

Is this multiple choice? I would be able to help if I could see a list of options :-)

6 0

3 years ago

Read 2 more answers

Which of the following statements accurately describes a series circuit? Select all that apply. The flow of electrons follow the

hammer [34]

In series connections, the flow of electrons follow the same path as the current remains constant in all the elements of the circuits.

And the total resistance of the circuit increases as more resistors are added to the circuit in serial manner.

Option A and D

<u>Explanation:</u>

A circuit consists of number of passive and active devices in it. And depending upon the connections between the passive devices, the flow of current and potential drop across them will be specified.

Like if the passive devices are connected parallel to each other, the current flow through each device will vary but the voltage drop will be same. Similarly, if the passive devices are connected in series, then the current flow will be constant in the devices but the potential drop will vary.

Thus, in series connections, the flow of electrons follow the same path as the current remains constant in all the elements of the circuits. And the total resistance of the circuit increases as more resistors are added to the circuit in serial manner.

8 0

3 years ago

Which one of the following scenarios accurately describes a condition in which resonance can occur?

mr Goodwill [35]

A pipe's length is equal to 1⁄2 of the wavelength of the sound waves produced by a tuning fork vibrating over one end of the pipe that's open to the air at both ends.

4 0

4 years ago

A 80 kg skier grips a moving rope that is powered by an engine and is pulled at constant speed to the top of a 25 degrees hill.

zloy xaker [14]

Answer:

$P=28.085\,hp$

Explanation:

Given that:

mass of 1 skier, $m=80kg$

inclination of hill, $\theta=25^{\circ}$

length of inclined slope, $l=220m$

time taken to reach the top of hill, $t=2.3 min= 138 s$

coefficient of friction, $\mu=0.15$

<em>Now, force normal to the inclined plane:</em>

$F_N=m.g.cos\theta$

$F_N=80\times 9.8\times cos25^{\circ}$

$F_N=710.54\,N$

<em>Frictional force:</em>

$f=\mu.F_N$

$f=0.15\times 710.54$

$f=106.58\,N$

<em>The component of weight along the inclined plane:</em>

$W_l=m.g.sin\theta$

$W_l=80\times 9.8\times sin25^{\circ}$

$W_l=331.33\,N$

<em>Now the total force required along the inclination to move at the top of hill:</em>

$F=f+W_l$

$F=106.58+331.33$

$F=437.91\,N$

<em>Hence the work done:</em>

$W=F.l$

$W=437.91\times 220$

$W=96340.80\,J$

<em>Now power:</em>

$P=\frac{W}{t}$

$P=\frac{96340.80}{138}$

$P=698.12\,W$

<u>So, power required for 30 such bodies:</u>

$P=30\times 698.12$

$P=20943.65\,W$

$P=\frac{20943.65}{745.7}$

$P=28.085\,hp$

8 0

3 years ago