<< Chapter < Page Chapter >> Page >

Conceptual questions

How is heat transfer related to temperature?

Temperature differences cause heat transfer.

Got questions? Get instant answers now!

Describe a situation in which heat transfer occurs.

Got questions? Get instant answers now!

When heat transfers into a system, is the energy stored as heat? Explain briefly.

No, it is stored as thermal energy. A thermodynamic system does not have a well-defined quantity of heat.

Got questions? Get instant answers now!

The brakes in a car increase in temperature by Δ T when bringing the car to rest from a speed v . How much greater would Δ T be if the car initially had twice the speed? You may assume the car stops fast enough that no heat transfers out of the brakes.

Got questions? Get instant answers now!

Problems

On a hot day, the temperature of an 80,000-L swimming pool increases by 1.50 ° C . What is the net heat transfer during this heating? Ignore any complications, such as loss of water by evaporation.

m = 5.20 × 10 8 J

Got questions? Get instant answers now!

To sterilize a 50.0-g glass baby bottle, we must raise its temperature from 22.0 ° C to 95.0 ° C . How much heat transfer is required?

Got questions? Get instant answers now!

The same heat transfer into identical masses of different substances produces different temperature changes. Calculate the final temperature when 1.00 kcal of heat transfers into 1.00 kg of the following, originally at 20.0 ° C : (a) water; (b) concrete; (c) steel; and (d) mercury.

Q = m c Δ T Δ T = Q m c ; a. 21.0 ° C ; b. 25.0 ° C ; c. 29.3 ° C ; d. 50.0 ° C

Got questions? Get instant answers now!

Rubbing your hands together warms them by converting work into thermal energy. If a woman rubs her hands back and forth for a total of 20 rubs, at a distance of 7.50 cm per rub, and with an average frictional force of 40.0 N, what is the temperature increase? The mass of tissues warmed is only 0.100 kg, mostly in the palms and fingers.

Got questions? Get instant answers now!

A 0.250 -kg block of a pure material is heated from 20.0 ° C to 65.0 ° C by the addition of 4.35 kJ of energy. Calculate its specific heat and identify the substance of which it is most likely composed.

Q = m c Δ T c = Q m Δ T = 1.04 kcal ( 0.250 kg ) ( 45.0 ° C ) = 0.0924 kcal/kg · ° C . It is copper.

Got questions? Get instant answers now!

Suppose identical amounts of heat transfer into different masses of copper and water, causing identical changes in temperature. What is the ratio of the mass of copper to water?

Got questions? Get instant answers now!

(a) The number of kilocalories in food is determined by calorimetry techniques in which the food is burned and the amount of heat transfer is measured. How many kilocalories per gram are there in a 5.00-g peanut if the energy from burning it is transferred to 0.500 kg of water held in a 0.100-kg aluminum cup, causing a 54.9 - ° C temperature increase? Assume the process takes place in an ideal calorimeter, in other words a perfectly insulated container. (b) Compare your answer to the following labeling information found on a package of dry roasted peanuts: a serving of 33 g contains 200 calories. Comment on whether the values are consistent.

a. Q = m w c w Δ T + m A1 c A1 Δ T = ( m w c w + m A1 c A1 ) Δ T ;
Q = [ ( 0.500 kg ) ( 1.00 kcal/kg · ° C ) + ( 0.100 kg ) ( 0.215 kcal/kg · ° C ) ] ( 54.9 ° C ) = 28.63 kcal ;
Q m p = 28.63 kcal 5.00 g = 5.73 kcal/g ; b. Q m p = 200 kcal 33 g = 6 kcal/g , which is consistent with our results to part (a), to one significant figure.

Got questions? Get instant answers now!

Following vigorous exercise, the body temperature of an 80.0 kg person is 40.0 ° C . At what rate in watts must the person transfer thermal energy to reduce the body temperature to 37.0 ° C in 30.0 min, assuming the body continues to produce energy at the rate of 150 W? ( 1 watt = 1 joule/second or 1 W = 1 J/s )

Got questions? Get instant answers now!

In a study of healthy young men JW Vezina, “An examination of the differences between two methods of estimating energy expenditure in resistance training activities,” Journal of Strength and Conditioning Research , April 28, 2014, http://www.ncbi.nlm.nih.gov/pubmed/24402448 , doing 20 push-ups in 1 minute burned an amount of energy per kg that for a 70.0-kg man corresponds to 8.06 calories (kcal). How much would a 70.0-kg man’s temperature rise if he did not lose any heat during that time?

0.139 ° C

Got questions? Get instant answers now!

A 1.28-kg sample of water at 10.0 ° C is in a calorimeter. You drop a piece of steel with a mass of 0.385 kg at 215 ° C into it. After the sizzling subsides, what is the final equilibrium temperature? (Make the reasonable assumptions that any steam produced condenses into liquid water during the process of equilibration and that the evaporation and condensation don’t affect the outcome, as we’ll see in the next section.)

Got questions? Get instant answers now!

Repeat the preceding problem, assuming the water is in a glass beaker with a mass of 0.200 kg, which in turn is in a calorimeter. The beaker is initially at the same temperature as the water. Before doing the problem, should the answer be higher or lower than the preceding answer? Comparing the mass and specific heat of the beaker to those of the water, do you think the beaker will make much difference?

It should be lower. The beaker will not make much difference: 16.3 ° C

Got questions? Get instant answers now!

Questions & Answers

what is mutation
Janga Reply
what is a cell
Sifune Reply
how is urine form
Sifune
what is antagonism?
mahase Reply
classification of plants, gymnosperm features.
Linsy Reply
what is the features of gymnosperm
Linsy
how many types of solid did we have
Samuel Reply
what is an ionic bond
Samuel
What is Atoms
Daprince Reply
what is fallopian tube
Merolyn
what is bladder
Merolyn
what's bulbourethral gland
Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
what is heart
Konadu Reply
how is urine formed in human
Konadu
how is urine formed in human
Rahma
what is the diference between a cavity and a canal
Pelagie Reply
what is the causative agent of malaria
Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
Olalekan
a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
Achor
how are lungs work
Commander
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
endocrine secrete hormone and regulate body process
Achor
while pituitary gland is an example of endocrine system and it's found in the Brain
Achor
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 7

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, University physics volume 2. OpenStax CNX. Oct 06, 2016 Download for free at http://cnx.org/content/col12074/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'University physics volume 2' conversation and receive update notifications?

Ask