# 13.1 Temperature  (Page 5/14)

 Page 5 / 14

This law was postulated in the 1930s, after the first and second laws of thermodynamics had been developed and named. It is called the zeroth law because it comes logically before the first and second laws (discussed in Thermodynamics ). An example of this law in action is seen in babies in incubators: babies in incubators normally have very few clothes on, so to an observer they look as if they may not be warm enough. However, the temperature of the air, the cot, and the baby is the same, because they are in thermal equilibrium, which is accomplished by maintaining air temperature to keep the baby comfortable.

Does the temperature of a body depend on its size?

No, the system can be divided into smaller parts each of which is at the same temperature. We say that the temperature is an intensive quantity. Intensive quantities are independent of size.

## Section summary

• Temperature is the quantity measured by a thermometer.
• Temperature is related to the average kinetic energy of atoms and molecules in a system.
• Absolute zero is the temperature at which there is no molecular motion.
• There are three main temperature scales: Celsius, Fahrenheit, and Kelvin.
• Temperatures on one scale can be converted to temperatures on another scale using the following equations:
${T}_{\text{º}\text{F}}=\frac{9}{5}{T}_{\text{º}\text{C}}+\text{32}$
${T}_{\text{º}\text{C}}=\frac{5}{9}\left({T}_{\text{º}\text{F}}-\text{32}\right)$
${T}_{\text{K}}={T}_{\text{º}\text{C}}+\text{273}\text{.}\text{15}$
${T}_{\text{º}\text{C}}={T}_{\text{K}}-\text{273}\text{.}\text{15}$
• Systems are in thermal equilibrium when they have the same temperature.
• Thermal equilibrium occurs when two bodies are in contact with each other and can freely exchange energy.
• The zeroth law of thermodynamics states that when two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system, C, then A is also in thermal equilibrium with C.

## Conceptual questions

What does it mean to say that two systems are in thermal equilibrium?

Give an example of a physical property that varies with temperature and describe how it is used to measure temperature.

When a cold alcohol thermometer is placed in a hot liquid, the column of alcohol goes down slightly before going up. Explain why.

If you add boiling water to a cup at room temperature, what would you expect the final equilibrium temperature of the unit to be? You will need to include the surroundings as part of the system. Consider the zeroth law of thermodynamics.

## Problems&Exercises

What is the Fahrenheit temperature of a person with a $\text{39}\text{.}0\text{º}\text{C}$ fever?

$\text{102}\text{º}\text{F}$

Frost damage to most plants occurs at temperatures of $\text{28}\text{.}0\text{º}\text{F}$ or lower. What is this temperature on the Kelvin scale?

To conserve energy, room temperatures are kept at $\text{68}\text{.}0\text{º}\text{F}$ in the winter and $\text{78}\text{.}0\text{º}\text{F}$ in the summer. What are these temperatures on the Celsius scale?

$\text{20}\text{.}0\text{º}\text{C}$ and $\text{25}\text{.}6\text{º}\text{C}$

A tungsten light bulb filament may operate at 2900 K. What is its Fahrenheit temperature? What is this on the Celsius scale?

The surface temperature of the Sun is about 5750 K. What is this temperature on the Fahrenheit scale?

$\text{9890}\text{º}\text{F}$

One of the hottest temperatures ever recorded on the surface of Earth was $\text{134}\text{º}\text{F}$ in Death Valley, CA. What is this temperature in Celsius degrees? What is this temperature in Kelvin?

(a) Suppose a cold front blows into your locale and drops the temperature by 40.0 Fahrenheit degrees. How many degrees Celsius does the temperature decrease when there is a $\text{40}\text{.}0\text{º}\text{F}$ decrease in temperature? (b) Show that any change in temperature in Fahrenheit degrees is nine-fifths the change in Celsius degrees.

(a) $\text{22}\text{.}2\text{º}\text{C}$

(b) $\begin{array}{lll}\text{Δ}T\left(\text{º}\text{F}\right)& =& {T}_{2}\left(\text{º}\text{F}\right)-{T}_{1}\left(\text{º}\text{F}\right)\\ & =& \frac{9}{5}{T}_{2}\left(\text{º}\text{C}\right)+\text{32}\text{.}0\text{º}-\left(\frac{9}{5}{T}_{1}\left(\text{º}\text{C}\right)+\text{32}\text{.}0\text{º}\right)\\ & =& \frac{9}{5}\left({T}_{2}\left(\text{º}\text{C}\right)-{T}_{1}\left(\text{º}\text{C}\right)\right)\text{}=\frac{9}{5}\text{Δ}T\left(\text{º}\text{C}\right)\end{array}$

(a) At what temperature do the Fahrenheit and Celsius scales have the same numerical value? (b) At what temperature do the Fahrenheit and Kelvin scales have the same numerical value?

Calculate the final velocity attained, when a ball is given a velocity of 2.5m/s, acceleration of 0.67m/s² and reaches its point in 10s. Good luck!!!
2.68m/s
Doc
vf=vi+at vf=2.5+ 0.67*10 vf= 2.5 + 6.7 vf = 9.2
babar
s = vi t +1/2at sq s=58.5 s=v av X t vf= 9.2
babar
how 2.68
babar
v=u+at where v=final velocity u=initial velocity a=acceleration t=time
Eklu
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the dimension of work and energy is ML2T2 find the unit of work and energy hence drive for work?
KgM2S2
Acquah
Two bodies P and Quarter each of mass 1000g. Moved in the same direction with speed of 10m/s and 20m/s respectively. Calculate the impulse of P and Q obeying newton's 3rd law of motion
kk
Doc
definition for wave?
A disturbance that travel from one medium to another and without causing permanent change to its displacement
Fagbenro
In physics, a wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport (Mass transfer). ... There are two main types ofwaves: mechanical and electromagnetic. Mechanicalwaves propagate through a physical matter, whose substance is being deformed
Devansh
K
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Doc
Thanks
Note: LINEAR MOMENTUM Linear momentum is defined as the product of a system’s mass multiplied by its velocity: size 12{p=mv} {}
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zalmia
Study of matter and energy
Fagbenro
physics is the science of matter and energy and their interactions
Acquah
physics is the technology behind air and matter
Doc
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Easy to learn
William
31. Calculate the initial (from rest) acceleration of a proton in a 5.00×106 N/C electric field (such as created by a research Van de Graaff). Explicitly show how you follow the steps in the Problem-Solving Strategy for electrostatics.
A tennis ball is projected at an angle and attains a range of 78. if the velocity is 30metres per second, calculate the angle
Shimolla
what friction
question on friction
Wisdom
the rubbing of one object or surface against another.
author
momentum is the product of mass and it's velocity.
Algayawi
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Edina
Friction is a force that exist between two objects in contact. e.g. friction between road and car tires.
Eklu
With regards to a shielded cable, is there an induced current on the shield when the center conductor is carrying an AC Current? What is the formula?
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Awoke
its phenomenon, an observable fact.
author
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Force is the cause and momentum is its effect.
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A force is a pull or a push on an object, causing an object to move or a moving object to stop.
Eklu
Find the velocity that make one full oscillation in 10 seconds and also makes 1.7meters in the same time
yes
Rafael
OK
Oluwaseun
17m/s
Eklu
17m/s
Gabriel
0.17
Devansh
17m/s
Harrison
how did you solve it
Acquah
t=10s a=1.7m v=? u=0 but v=u+at but u=0 v=at 1.7×10=17 v=17m/s that's how I solved it.
Eklu
kk
Acquah
How is a=1.7m?
El
a is an acceleration
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Doc
its relating to time and oscillation made.
Eklu
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El
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A voltmeter is a device use in measuring electric potential in a volt.
Find out the equation of a simple harmonic progressive wave that have 0.2m with a frequency of 550hertz.If the wave moves along a positive x axis with the speed of 330m/s