Musk is working on developing reusable rockets in order to further us as a space-faring civilization. Given his life dedication to energy production, conservation, and efficiency, can you think of any other reasons that Musk may want to expand our ability to exist on other planets and in space?

Answer:

Conduction is a heat transfer mechanism. It is the dominant heat transfer mechanism in solids and it involves the vibration of the molecules of the solid. As heat is transfered to one end of the solid, the molecules at that end start to vibrate and in this process, collides with the adjacent molecules setting it to vibrate too. Also free electrons around the solid atoms (especially in metals) contribute to this heat flow. The continuous vibration is transfered from molecule to molecule gradually along the solid until the average kinetic energy (a measure of temperature) of the molecules along the metal has increased.

Convection is the dominant heat transfer mechanism in fluids, it involves the complete movement of the fluid molecule from a hot spot in the fluid to a cooler spot in the fluid. For convectional movement to occur, the molecules must first come in contact with the heat and absorb the heat first by conduction. As the heat increases, the fluid molecules break from just vibrating about a fixed point to moving completely to a cooler spot due to buoyant forces (due to the difference in density of hot and cooler fluid molecules). This clearly point out the fact that convectional heat transfer is first conduction, and then complete later flow of the fluid molecules.

The temperature drop of air if air is assumed to be an ideal gas for which C_p = ⁷/₂R is; Δt = 1546 K

We are given;

Final velocity; v₂ = 300 m/s

C_p = ⁷/₂R

At constant pressure, the change in enthalpy is;

Δh = C_p × Δt

Now, from first law of thermodynamics;

h₂ + (v₂²/2) = h₁ + (v₁²/2)

We are told initial velocity is negligible and as such v₁ = 0 m/s

Thus;

h₂ + (v₂²/2) = h₁ + 0

(h₁ - h₂) =  (v₂²/2)

Thus; Δh = v₂²/2

Finally;

C_p × Δt = v₂²/2

Δt = v₂²/2/(C_p)

Δt =  (300²/2)/(⁷/₂R)

where R is ideal gas constant = 8.314 Kj/kg.mol

Thus;

Δt = (300²/2)/(⁷/₂ × 8.314)

Δt = 1546 K

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Answer:

ΔH+U²/2=0

and

ΔH=×ΔT

∴to get the temperature drop of air, you make ΔT subject of the formula

ΔT=-U²/2Cp

    =-300²/2××8.314

∴ΔT=-1546K

Explanation:

Answer:

Explanation:

The specific heat for watermelon above freezing point is . The heat liberated by the watermelon to cool down to 8°C is:

The heat absorbed by the household refrigerator is:

Time needed to cool the watermelons is:

Explanation:

Step1

Absolute pressure is the pressure above zero level of the pressure. Absolute pressure is considering atmospheric pressure in it. Absolute pressure is always positive. There is no negative absolute pressure.

The expression for absolute pressure is given as follows:

Here, is absolute pressure, is gauge pressure and is atmospheric pressure.

Step2

Gauge pressure is the pressure that measure above atmospheric pressure. It is not considering atmospheric pressure. It can be negative called vacuum or negative gauge pressure. Gauge pressure used to simplify the pressure equation for fluid analysis.  

Answer:

(a) ΔU = 125 kJ

(b) ΔU = -110 kJ

Explanation:

(a) Suppose that 150 kJ of work are used to compress a spring, and that 25 kJ of heat are given off by the spring during this compression. What is the change in internal energy of the spring during the process?

The work is done to the system so w = 150 kJ.

The heat is released by the system so q = -25 kJ.

The change in internal energy (ΔU) is:

ΔU = q + w

ΔU = -25 kJ + 150 kJ = 125 kJ

(b) Suppose that 100 kJ of work is done by a motor, but it also gives off 10 kJ of heat while carrying out this work. What is the change in internal energy of the motor during the process?

The work is done by the system so w = -100 kJ.

The heat is released by the system so q = -10 kJ.

The change in internal energy (ΔU) is:

ΔU = q + w

ΔU = -10 kJ - 100 kJ = -110 kJ

Answer: D all above

Explanation:

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