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bonufazy [111]
3 years ago
5

On a hot summer day, a student turns his fan on when he leaves his room in the morning. When he returns in the evening, will the

room be warmer or cooler than the neighboring rooms? Why? Assume all the doors and windows are kept closed.
Engineering
1 answer:
Virty [35]3 years ago
5 0

Answer:

When the student returns, it will be hotter

Explanation:

We know that the room is closed, so no air is coming in from outside and no air goes outside as the windows and doors are closed. We know the fan is moving and the fan does not cool the air, it only moves the air. Therefore, this process creates kinetic energy that is converted into heat energy (internal) so that room begins to get warmer.

And we know by the the law of Conservation of Energy, there is no loss in energy

So, the room just gets hotter.

You might be interested in
A motorcycle starts from rest with an initial acceleration of 3 m/s^2, and the acceleration then changes with the distance s as
katrin2010 [14]

Answer:

Follows are the solution to this question:

Explanation:

Calculating the area under the curve:  

A = as

   =\frac{1}{2}(3 +6 \frac{m}{s^2})(100 \ m)+ \frac{1}{2}(6+4 \frac{m}{s^2})(100 m) \\\\=\frac{1}{2}(9 \frac{m}{s^2})(100 \ m)+ \frac{1}{2}(10\frac{m}{s^2})(100 m) \\\\=\frac{1}{2}(900 \frac{m^2}{s^2})+ \frac{1}{2}(1,000\frac{m^2}{s^2}) \\\\=(450 \frac{m^2}{s^2})+ (500\frac{m^2}{s^2}) \\\\= 950 \ \frac{m^2}{s^2}

Calculating the kinematics equation:

\to v^2 = v^2_{o} + 2as\\\\

        =0+ \sqrt{2as}\\\\ = \sqrt{2(A)}\\\\= \sqrt{2(950 \frac{m^2}{s^2})}\\\\= 43.59 \frac{m}{s}

Calculating the value of acceleration:  

\to a= \frac{dv}{dt}

=\frac{dv}{ds}(\frac{ds}{dt}) \\\\=v\frac{dv}{ds}\\\\\to \frac{dv}{ds}=\frac{a}{v}

\to \frac{dv}{ds} =\frac{4 \frac{m}{s^2}}{43.59 \frac{m}{s}} \\\\

         =\frac{0.092}{s}

3 0
2 years ago
The constant-pressure specific heat of air at 25°C is 1.005 kJ/kg·°C. Express this value in kJ/kg·K, J/g·°C, kcal/ kg·°C, and Bt
Dmitry [639]

Answer:

a) C_v = 1.005 KJ/kgK

b) C_v = 1005.000 J/kgC

c) C_v = 0.240 kcal/kgC

d) C_v = 0.240 Btu/lbmF

Explanation:

Given:

- constant-pressure specific heat C_v = 1.005 KJ/kgC

Find C_v in units of:

a) kJ/kg·K

b) J/g·°C

c) kcal/ kg·°C

d) Btu/lbm·°F

Solution:

a) C_v is Specific heat capacity is the quantity of heat needed to raise the temperature per unit mass. Usually, it's the heat in Joules needed to raise the temperature of 1 gram of sample 1 Kelvin or 1 degree Celsius. Hence,

C_v = 1.005 KJ/kgK

b)

                           C_v = 1.005 KJ/kgC * ( 1000 J / KJ)

                           C_v = 1005.000 J/kgC

c)

                           C_v = 1.005 KJ/kgC * ( 0.239006 kcal / KJ)

                           C_v = 0.240 kcal/kgC

d)

C_v = 1.005 KJ/kgC * ( 0.947817 Btu / KJ) * ( kg / 2.205 lbm)*(Δ1 C / Δ1.8 F)

C_v = 0.240 Btu/lbmF

6 0
3 years ago
What is the value of the magicPowers variable after executing the following code snippet? String magicPowers = ""; int experienc
Evgen [1.6K]

Answer:

Shining lantern Magic beans                

Explanation:

I will explain the code line by line.

The first statement contains a string type variable magicPowers and second statement has an int type variable experienceLevel which is initialized by value 9.

Nested if statement are used and lets see which of those statements execute.

The first if statement checks if the value of experienceLevel is greater than 10. This statement evaluates to false because the value of experienceLevel is set to 9. Then the program control moves to the next if statement.

The second if statement checks if the value of experienceLevel is greater than 8. This if condition evaluates to true because the value of experienceLevel  is 9. So this if statement is executed which contains the statement magicPowers = magicPowers + "Shining lantern "; . This means magicPowers stores the string Shining lantern.

The third if statement checks if the value of experienceLevel  is greater than 2. As the value of experienceLevel  is 9 so this condition also evaluates to true which means the statement magicPowers = magicPowers + "Magic beans "; is executed. This statement means magicPowers stores the string Magic Beans

You can use a print statement to display the output on the screen as:

System.out.print(magicPowers);

Output:

Shining lantern Magic beans        

The program along with the output is attached as a screenshot.

5 0
3 years ago
Which phrase best describes a safety-critical system?
MAVERICK [17]

Answer:

Life critical systems or computer systems that cause harm to people

4 0
3 years ago
1.00-L insulated bottle is full of tea at 90.08°C. You pour out one cup of tea and immediately screw the stopper back on the bot
elixir [45]

Answer:

T_{f} = 90.07998 ° C

Explanation:

This is a calorimetry process where the heat given by the Te is absorbed by the air at room temperature (T₀ = 25ºC) with a specific heat of 1,009 J / kg ºC, we assume that the amount of Tea in the cup is V₀ = 100 ml. The bottle being thermally insulated does not intervene in the process

                 Qc = -Qb

                M c_{e_Te} (T₁ -T_{f}) = m c_{e_air} (T_{f}-T₀)

Where M is the mass of Tea that remains after taking out the cup, the density of Te is the density of water plus the solids dissolved in them, the approximate values are from 1020 to 1200 kg / m³, for this calculation we use 1100 kg / m³

   ρ = m / V  

   V = 1000 -100 = 900 ml  

   V = 0.900 l (1 m3 / 1000 l) = 0.900 10⁻³ m³  

   V_air = 0.100 l = 0.1 10⁻³ m³  

Tea Mass  

     M = ρ V_te  

     M = 1100 0.9 10⁻³  

     M = 0.990 kg  

Air mass  

     m = ρ _air V_air  

     m = 1.225 0.1 10⁻³  

     m = 0.1225 10⁻³ kg  

(m c_{e_air} + M c_{e_Te}) T_{f}. = M c_{e_Te} T1 - m c_{e_air} T₀  

T_{f} = (M c_{e_Te} T₁ - m c_{e_air} T₀) / (m c_{e_air} + M c_{e_Te})  

Let's calculate  

T_{f} = (0.990 1100 90.08– 0.1225 10⁻³ 1.225 25) / (0.1225 10⁻³ 1.225 + 0.990 1100)  

T_{f} = (98097.12 -3.75 10⁻³) / (0.15 10⁻³ +1089)  

T_{f} = 98097.11 / 1089.0002  

T_{f} = 90.07998 ° C  

This temperature decrease is very small and cannot be measured

5 0
3 years ago
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