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kiruha [24]
3 years ago
11

The air contained in a room loses heat to the surroundings at a rate of 50 kJ/min while work is supplied to the room by computer

, TV, and lights at a rate of 1.2 kW. What is the net amount of energy change of the air in the room during a 30-min period?

Engineering
2 answers:
Mkey [24]3 years ago
8 0

Answer:

660KJ

Explanation:

Given

Let Q = Heat Loss from room = 50kj/min

Let W = Work Supplied to room = 1.2KW

1 kilowatt = 1 kilojoules per second

So, W = 1.2KJ/s

In heat and work (Sign Convention)

We know that

1. Heat takes positive sign when it is added to the system

2. Heat takes negative sign when it is removed from the system.

3. Work done is considered positive when work is done by the system

4. Work done is considered negative when work is done on the system.

From the above illustration, heat loss (Q) = -50KJ/Min

In 30 minutes time, Q = -50Kj/Min * 30 Min

Work done in 30 minutes = -1500 KJ

Also, work supplied = -1.2Kj/s

Work supplied to the system in 30 minutes = -1.2Kj/s * 30 minutes

W = -1.2 KJ/s * 30 * 60 seconds

W = -2160KJ

In thermodynamics (First Law)

Q = W + ΔU

-1500 = -2160 + ΔU

∆U = 2160 - 1500

∆U = 660KJ

Artemon [7]3 years ago
4 0

Answer:

net amount of energy change of the air in the room during a 30-min period = 660KJ

Explanation:

The detailed calculation is as shown in the attached file.

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The thematic group governing the behavior of dynamic system is control system, and the one packaging the miniature components to conduct electricity is electronic system. Thus, option E is correct.

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Explanation:

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4 0
3 years ago
1. The area(in square centimeters) of a square coaster can be represented by
Brrunno [24]

Answer: (d−4) 2

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The first term is,  d2  its coefficient is  1 .

The middle term is,  -8d  its coefficient is  -8 .

The last term, "the constant", is  +16

Step-1 : Multiply the coefficient of the first term by the constant   1 • 16 = 16

Step-2 : Find two factors of  16  whose sum equals the coefficient of the middle term, which is   -8 .

     -16    +    -1    =    -17

     -8    +    -2    =    -10

     -4    +    -4    =    -8    That's it

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above,  -4  and  -4

                    d2 - 4d - 4d - 16

Step-4 : Add up the first 2 terms, pulling out like factors :

                   d • (d-4)

             Add up the last 2 terms, pulling out common factors :

                   4 • (d-4)

Step-5 : Add up the four terms of step 4 :

                   (d-4)  •  (d-4)

            Which is the desired factorization

  Multiply  (d-4)  by  (d-4)

The rule says : To multiply exponential expressions which have the same base, add up their exponents.

In our case, the common base is  (d-4)  and the exponents are :

         1 , as  (d-4)  is the same number as  (d-4)1

and   1 , as  (d-4)  is the same number as  (d-4)1

The product is therefore,  (d-4)(1+1) = (d-4)2

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