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Ainat [17]
2 years ago
14

the water behind hoover dam in nevada is 206 m higher than the colorado river below it. at what rate must water pass through the

hydraulic turbines of this dam to produce 100 mw of power if the turbines are 100 percent efficient
Physics
1 answer:
Nitella [24]2 years ago
5 0

Answer:

the required mass flow rate is 49484.37 kg/s

Explanation:

Given the data in the question;

we first determine the relation for mass flow rate of water that passes through the turbine;

so the relation for net work on the turbine due to the change in potential energy considering 100% efficiency is;

W_{net} = m ( Δ P.E )

so we substitute (gh) for ( Δ P.E );

W_{net} = m (gh)

m = W_{net} / gh

so we substitute our given values into the equation

m = 100 MW / ( 9.81 m/s²) × 206 m

m = ( 100 MW × 10⁶W/MW) / ( 9.81 m/s²) × 206 m

m = 10 × 10⁷ / 2020.86

m = 49484.37 kg/s

Therefore, the required mass flow rate is 49484.37 kg/s

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Three balls with the same radius 21 cm are in water. Ball 1 floats, with
Masteriza [31]

Answer:

Explanation:

A )

The ball floats with half of it exposed above the water level . So it must have density half that of water . In other words its density must have been 500 kg / m³

B )

Tension in the ball will be equal to net force acting on the ball

Net force on the ball = buoyant force - weight .

4/3 x π x .21³ x 10⁻⁶ x 9.8 ( 1000 - 893 )

= 40.65 x 10⁻⁶ N .

C )Tension in the 3 rd  ball will be equal to net force acting on the ball

Net force on the ball =  weight  - buoyant force

= 4/3 x π x .21³ x 10⁻⁶ x 9.8 ( 1320 - 1000  )

=  121.6  x 10⁻⁶ N .

7 0
2 years ago
If the surface temperature of that person's skin is 30∘C (that's a little lower than healthy internal body temperature becaus
anastassius [24]

Answer:

E=477.92\ W.m^{-2}

Explanation:

Given that:

Absolute temperature of the body, T=273+30=303\ K

  • emissivity of the body, \epsilon=1

<u>Using Stefan Boltzmann Law of thermal radiation:</u>

E=\epsilon. \sigma.T^4

where:

\sigma =5.67\times 10^{-8}\ W.m^{-2}.K^{-4}   (Stefan Boltzmann constant)

Now putting the respective values:

E=1\times 5.67\times 10^{-8}\times 303^4

E=477.92\ W.m^{-2}

5 0
2 years ago
Shareen performs a skit to model a method of charging. In the skit, a painter shakes her hand and gets paint on her.
Veseljchak [2.6K]

Answer:

It models conduction because the painter represents a charged object and the paint represents electrons that are transferred through contact.

Explanation:

Conduction phenomenon of charging is the process of charging in which two bodies are made in contact with each other so that charges are transferred due to potential difference of two bodies.

here we know that when hands are shake then it will have paint on it. so here due to hand shake the hands are in contact with charge particles and due to contact the electrons are transferred to the hand.

Now here we need to assume that charge of paint must be opposite that of the charge on the hand because only due to opposite charge attraction the paint must be transferred to the hand

SO here correct answer will be

It models conduction because the painter represents a charged object and the paint represents electrons that are transferred through contact.

5 0
2 years ago
Read 2 more answers
An electric heater draws a steady current = 20.0 A on a 120-V line. (a) Calculate how much power does it require.
babymother [125]

Answer:

The heater power required is 2400 W. The power in the heater can be calculated as the product of the voltage line and the steady current:

P=V.I

P=120 V * 20 A = 2400 VA = 2400 W

Explanation:

8 0
2 years ago
A circular saw blade with radius 0.175 m starts from rest and turns in a vertical plane with a constant angular acceleration of
ANEK [815]

Answer:

The distance the piece travel in horizontally axis is

L=3.55m

Explanation:

a=2 \frac{rev}{s^{2}} \\h=0.820m\\r = 0.125 m&#10;\\d=150rev

d= 155 rev = 155(2\pi ) = 310\pi rad

a= 2.0 \frac{rev}{s^{2} } = 2.0(2\pi )  = 4.0\pi \frac{rev}{s^{2} }

d=d_{i}+vo*t+\frac{1}{2}*a*t^{2} \\ di=0\\vo=0\\d=\frac{1}{2}*a*t^{2}\\t=\sqrt{\frac{2*d}{a}}\\t=\sqrt{\frac{2*310 rad}{4\frac{rad}{s^{2}}}} \\t=12.449

w=a*t\\w=4\frac{rad}{s^{2}}*12.449s\\ w=49.79 \frac{rad}{s}

Now the angular velocity is the blade speed so:

V=w*r\\V=49.79 \frac{rad}{s}*0.175m\\V=8.7 \frac{m}{s}

assuming no air friction effects affect blade piece:

time for blade piece to fall to floor

t=\sqrt{\frac{2*h}{g}}\\t=\sqrt{\frac{2*0.820m}{9.8\frac{m}{s^{2} } }}\\t=0.409s

Now is the same time the piece travel horizontally

L=t*V\\L=0.409s*8.7\frac{m}{s}\\L=3.55m

blade piece travels  HORIZONTALLY = (24.5)(0.397) = 9.73 m  ANS

6 0
2 years ago
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