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3 years ago

Which of these individuals has a sedentary lifestyle

Physics

1 answer:

xz_007 [3.2K]3 years ago

4 0

Answer:

Explanation:

A sedentary lifestyle is someone that does not participate in physical activities. Leslie is not active and plays video games instead.

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Air enters a turbine operating at steady state with a pressure of 75 Ibf/in.^2, a temperature of 800º R and velocity of 400 ft/s

Arturiano [62]

Answer:

(a) W/m = 49.334 Btu/lb

(b) $\frac{E_{d} }{m}$ = 22.12 Btu/lb

Explanation:

For the given problem, it can be assumed that the system is operating at steady state and the effects of potential energy can be neglected.

(a) Using the thermodynamic table for air.

At the temperature ( $T_{1}$ )of 800 ºR and pressure ( $P_{1}$ ) of 75 Ibf/in.^2, we can deduce that:

Specific enthalpy ( $h_{1}$ ) = 191.81 BTu/lb

Specific entropy ( $s_{1}$ ) = 0.6956 Btu/(lb.ºR)

At the temperature ( $T_{2}$ )of 600 ºR and pressure ( $P_{2}$ ) of 15 Ibf/in.^2, we can deduce that:

Specific enthalpy ( $h_{2}$ ) = 143.47 BTu/lb

Specific entropy ( $s_{2}$ ) = 0.6261 Btu/(lb.ºR)

The work done can be calculated using energy rate equation:

$\frac{W}{m} = \frac{Q}{m} + (h_{1} - h_{2}) + \frac{V_{1}^{2} - V_{2}^{2}}{2}$

Q/m = heat transfer = -2 Btu/lb

$V_{1}$ = 400 ft/s

$V_{2}$ = 100 ft/s

$\frac{W}{m} = -2 + (191.81 - 143.47) + \frac{400^{2} - 100^{2}}{2}*[tex]\frac{1}{2*32.2*778}$ [/tex] = -2 + 48.34 + 29.938 = 49.334 Btu/lb

(b) To calculate the exergy destruction, we will use the equation for exergy rate:

$\frac{E_{d} }{m} = [1-\frac{T_{o} }{T_{b} }](\frac{Q}{m}) - \frac{W}{m} + [(h_{1} - h_{2}) -T_{o}(s_{1} - s_{2}) + \frac{V^{2} _{1} - V_{2} ^{2}}{2}]$

The equation above is further simplified to:

$\frac{Ed}{m} = T_{o}[(s_{2} -s_{1}) - Rln\frac{P_{2} }{P_{1} } - \frac{Q/m}{T_{b} }]$

Using a reference temperature (To) = 500 °R

Average surface temperature (Tb = 620°R

$\frac{Ed}{m} = 500*[(0.6261 -0.6956) - (1.986/28.97)ln\frac{15 }{75 } - \frac{-2}{620}}]$

$\frac{E_{d} }{m}$ = 500*[-0.0695 +0.068688*1.609 +0.003225] = 22.12 Btu/lb

5 0

3 years ago

It's for #8....I know the answer is 293.2 ft I just don't know how to get it

Oksi-84 [34.3K]

Kinectic Energy=1/2(mass)(velocity)^2 so 1.2=1/2(.0012)(position/2) so it travels 4000 m. Not sure how it is 293.2 ft

7 0

2 years ago

What is tarzan's speed vf just before he reaches jane? express your answer in meters per second to two significant figures?

e-lub [12.9K]

Before swinging, T has only potential energy, (no speed)
Ui = mgh
Where h is the vertical displacement of T
From the laws of geometry,
cos45 = (L-h)/L
cos45 = 1-h/L
h/L = 1-cos45
h = L(1-cos45)

Therefore
Ui = mgL(1-cos45)

Proceeding the same way,
Twill raise to aheight of h' due to swing
h' = L(1-cos30)
The PE of T after swing is
Uf = mgh'
Uf = mgL(1-cos30)

Along with the PE , T has some kinetic energy results due to the moment.
Tf = 0.5*mv^2

According to the law of conservation of energy,
Ui = Uf+Tf
mgL(1-cos45) = mgL(1-cos30) + 0.5*mv^2
gL(co30-cos45) = 0.5*v^2
9.8*20*(co30-cos45) = 0.5*V^2
v = 7.89 m/s

<span>The speed f T after swing is 7.89 m/s</span>

3 0

3 years ago

Heat is the transfer of thermal energy from one object to another because of a difference in

evablogger [386]

The Answer Is Temprature. Hope This Helps :)

8 0

3 years ago

Read 2 more answers

If a 20 gram bird and a 0.001 gram mosquito are moving at the same speed, which has the higher kinetic energy?why?

MissTica

Answer:

The bird has 20,000 times higher kinetic energy than the mosquito.

Explanation:

The formula for kinetic energy shows that the amount of energy is proportional to the mass:

$E_k=\frac{1}{2}mv^2$

The velocity of both objects being the same, the mass is the determiner. The ratio of the kinetic energy of the bird and the mosquito then becomes the ratio of their masses, i.e., 0.02kg/0.00001kg. The bird's energy is 20,000 times higher than that of the mosquito. This proportion becomes more believable if you imagine the event of a distracted errant bird colliding with your head, versus a confused mosquito colliding with your head.

8 0

3 years ago