A 1.0kgball is at rest on the floor in a2.0m×2.0m×2.0m room of air at STP. Air is80% nitrogen (N2)and20% oxygen(O2) by volume.
a. What is the thermal energy of the air in the room?
b. What fraction of the thermal energy would have to be conveyed to the ball for it to be spontaneously launched to a height of1.0m ?
c. By how much would the air temperature have to decrease to launch the ball?
d. Your answer to part c is so small as to be unnoticeable, yet this event never happens. Why not?

Short Answer

Expert verified

aThe thermal energy of air in the room is2MJ;

bThe Fraction of thermal energy is4.9106;

cThe air temperature decreases atlocalid="1648536068001" 1.4mK;

dThe molecules in the ball move in all directions equally.

Step by step solution

01

Step: 1  Finding thermal energy: (part a)

The energy can be distributed in a variety of ways.

E=52nRT

The number nof moles from the ideal gas law,

pV=nRTn=pVRT pV=nRTn=pVRT

The energy can be expressed in a variety of ways.

E=52pV

The degree of freedom are 5.

E=521058=2106J.

02

Step: 2  Finding the fraction of thermal energy: (part b)

The work needed will be,

W=mgh=19.81=9.8J

Our required ratio is,

R=9.82106=4.9106.

03

Step: 3 c and d Change in temperature: (part c and d)

We've recently calculated the proportion of energy required for our job to overall energy. The energy is linearly related to the temperature, as we observed in the first equation. This means that the temperature, energy, and energy change will be supplied to the temperature, energy, and energy change, respectively.

ΔT=RT.

ΔT=4.9106273=0.00014K.

(d)The momentum that the ball receives from the air raises the energy of all molecules. Because these molecules fly in random directions, they have no effect on the ball's movement. The ball would move if they all moved in the same direction.

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Most popular questions from this chapter

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