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3 years ago

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Which statement describes a benefit of a model that uses three balls to model the Sun-Earth-Moon system? A. Every aspect of the

solar system can be modeled by the balls. B. It can be used to represent motions that are too fast to be studied easily 11 C. The only information shown is how eclipses happen. D. It represents a very large, complex system.

1 answer:

Dovator [93]3 years ago

8 0

Answer:

D. It represents a very large, complex system.

Explanation:

I just did it on a p e x...

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An object that is farther from a converging lens than its focal point always has an image that is _____.

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Smaller in size (Pt. Sized)

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Suppose you test a gas in the laboratory. You learn that the gas is made up of carbon atoms and oxygen atoms. Is the gas a compo

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Which of these accurately identify characteristics of light and mechanical waves? Select the TWO (2) that apply.

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The two correct statement are A and B. Light waves are electromagnetic waves that can travel through a vacuum. Mechanical waves can travel through a vacuum.

<h3>What is an electromagnetic wave?</h3>

EM waves are the electromagnetic radiations are made up of electromagnetic waves created when an electric field collides with a magnetic field.

Electromagnetic waves may alternatively be defined as the combination of oscillating electric and magnetic fields.

Electrically charged particles experiencing acceleration create electromagnetic waves, which can then interact with other charged particles and exert force on them.

The two correct statement is;

1. Light waves are electromagnetic waves that can travel through a vacuum.

2. Mechanical waves can travel through a vacuum.

Hence,two correct statement are A and B.

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2 years ago

Consider atmospheric air at 20°C and a velocity of 30 m/s flowing over both surfaces of a 1-m-long flat plate that is maintained

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3 years ago

Steam enters an adiabatic turbine steadily at 7 MPa, 5008C, and 45 m/s, and leaves at 100 kPa and 75 m/s. If the power output of

marusya05 [52]

Answer:

a) $\dot m = 6.878\,\frac{kg}{s}$ , b) $T = 104.3^{\textdegree}C$ , c) $\dot S_{gen} = 11.8\,\frac{kW}{K}$

Explanation:

a) The turbine is modelled by means of the First Principle of Thermodynamics. Changes in kinetic and potential energy are negligible.

$-\dot W_{out} + \dot m \cdot (h_{in}-h_{out}) = 0$

The mass flow rate is:

$\dot m = \frac{\dot W_{out}}{h_{in}-h_{out}}$

According to property water tables, specific enthalpies and entropies are:

State 1 - Superheated steam

$P = 7000\,kPa$

$T = 500^{\textdegree}C$

$h = 3411.4\,\frac{kJ}{kg}$

$s = 6.8000\,\frac{kJ}{kg\cdot K}$

State 2s - Liquid-Vapor Mixture

$P = 100\,kPa$

$h = 2467.32\,\frac{kJ}{kg}$

$s = 6.8000\,\frac{kJ}{kg\cdot K}$

$x = 0.908$

The isentropic efficiency is given by the following expression:

$\eta_{s} = \frac{h_{1}-h_{2}}{h_{1}-h_{2s}}$

The real specific enthalpy at outlet is:

$h_{2} = h_{1} - \eta_{s}\cdot (h_{1}-h_{2s})$

$h_{2} = 3411.4\,\frac{kJ}{kg} - 0.77\cdot (3411.4\,\frac{kJ}{kg} - 2467.32\,\frac{kJ}{kg} )$

$h_{2} = 2684.46\,\frac{kJ}{kg}$

State 2 - Superheated Vapor

$P = 100\,kPa$

$T = 104.3^{\textdegree}C$

$h = 2684.46\,\frac{kJ}{kg}$

$s = 7.3829\,\frac{kJ}{kg\cdot K}$

The mass flow rate is:

$\dot m = \frac{5000\,kW}{3411.4\,\frac{kJ}{kg} -2684.46\,\frac{kJ}{kg}}$

$\dot m = 6.878\,\frac{kg}{s}$

b) The temperature at the turbine exit is:

$T = 104.3^{\textdegree}C$

c) The rate of entropy generation is determined by means of the Second Law of Thermodynamics:

$\dot m \cdot (s_{in}-s_{out}) + \dot S_{gen} = 0$

$\dot S_{gen}=\dot m \cdot (s_{out}-s_{in})$

$\dot S_{gen} = (6.878\,\frac{kg}{s})\cdot (7.3829\,\frac{kJ}{kg\cdot K} - 6.8000\,\frac{kJ}{kg\cdot K} )$

$\dot S_{gen} = 11.8\,\frac{kW}{K}$

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4 years ago