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3 years ago

7

A typical student listening attentively to a physics lecture has a heat output of 100 w . how much heat energy does a class of 1

70 physics students release into a lecture hall over the course of a 50 min lecture?

1 answer:

nexus9112 [7]3 years ago

7 0

Since each student emits 100 W, so 170 students will emit:

total heat = 100 W * 170 = 17,000 W

Convert minutes to seconds:

time = 50 min * (60 s / min) = 3000 s

The energy is therefore:

E = 17,000 W * 3000 s

<span>E = 51 x 10^6 J = 51 MJ</span>

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Which statement correctly describes these electric field lines

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Its traveling in the +x direction

Explanation:

The E-field is in the +y-direction, and the B-field is in the +z-direction, so it must be moving along the +x-direction, since the E-field, B-field and the direction of moving are all at right angles to each other.

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Air enters a turbine operating at steady state at 8 bar, 1600 K and expands to 0.8 bar. The turbine is well insulated, and kinet

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Answer:

the maximum theoretical work that could be developed by the turbine is 775.140kJ/kg

Explanation:

To solve this problem it is necessary to apply the concepts related to the adiabatic process that relate the temperature and pressure variables

Mathematically this can be determined as

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Where

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Pressure at exit of turbine

Pressure at exit of turbine

The steady flow Energy equation for an open system is given as follows:

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Where,

m = mass

m(i) = mass at inlet

m(o)= Mass at outlet

h(i)= Enthalpy at inlet

h(o)= Enthalpy at outlet

W = Work done

Q = Heat transferred

v(i) = Velocity at inlet

v(o)= Velocity at outlet

Z(i)= Height at inlet

Z(o)= Height at outlet

For the insulated system with neglecting kinetic and potential energy effects

$h_i = h_0 + WW = h_i -h_0$

Using the relation T-P we can find the final temperature:

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

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From this point we can find the work done using the value of the specific heat of the air that is 1,005kJ / kgK

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the maximum theoretical work that could be developed by the turbine is 775.140kJ/kg

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Answer:

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$h_d=17.8\times t - 4.9t^2$

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