# 14.2 Temperature change and heat capacity  (Page 5/6)

 Page 5 / 6

## Conceptual questions

What three factors affect the heat transfer that is necessary to change an object’s temperature?

The brakes in a car increase in temperature by $\text{Δ}T$ when bringing the car to rest from a speed $v$ . How much greater would $\text{Δ}T$ be if the car initially had twice the speed? You may assume the car to stop sufficiently fast so that no heat transfers out of the brakes.

## Problems&Exercises

On a hot day, the temperature of an 80,000-L swimming pool increases by $1\text{.}\text{50ºC}$ . What is the net heat transfer during this heating? Ignore any complications, such as loss of water by evaporation.

$5\text{.}\text{02}×{\text{10}}^{8}\phantom{\rule{0.25em}{0ex}}\text{J}$

Show that $1\phantom{\rule{0.25em}{0ex}}\text{cal/g}\cdot \text{ºC}=1\phantom{\rule{0.25em}{0ex}}\text{kcal/kg}\cdot \text{ºC}$ .

To sterilize a 50.0-g glass baby bottle, we must raise its temperature from $\text{22}\text{.}0\text{ºC}$ to $\text{95}\text{.}0º\text{C}$ . How much heat transfer is required?

$\text{3.}\text{07}×{\text{10}}^{3}\phantom{\rule{0.25em}{0ex}}\text{J}$

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 $\text{20}\text{.}0º\text{C}$ : (a) water; (b) concrete; (c) steel; and (d) mercury.

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.

$0\text{.}\text{171º}\text{C}$

A 0.250-kg block of a pure material is heated from $\text{20}\text{.}0º\text{C}$ to $\text{65}\text{.}0º\text{C}$ by the addition of 4.35 kJ of energy. Calculate its specific heat and identify the substance of which it is most likely composed.

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?

10.8

(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 $\text{54}\text{.}9º\text{C}$ temperature increase? (b) Compare your answer to labeling information found on a package of peanuts and comment on whether the values are consistent.

Following vigorous exercise, the body temperature of an 80.0-kg person is $\text{40}\text{.}0º\text{C}$ . At what rate in watts must the person transfer thermal energy to reduce the the body temperature to $\text{37}\text{.}0º\text{C}$ in 30.0 min, assuming the body continues to produce energy at the rate of 150 W? $\left(\text{1 watt = 1 joule/second or 1 W = 1 J/s}\phantom{\rule{0.25em}{0ex}}\right)$ .

617 W

Even when shut down after a period of normal use, a large commercial nuclear reactor transfers thermal energy at the rate of 150 MW by the radioactive decay of fission products. This heat transfer causes a rapid increase in temperature if the cooling system fails $\left(\text{1 watt = 1 joule/second or 1 W = 1 J/s and 1 MW = 1 megawatt}\right)$ . (a) Calculate the rate of temperature increase in degrees Celsius per second $\left(\text{ºC/s}\right)$ if the mass of the reactor core is $1\text{.}\text{60}×{\text{10}}^{5}\phantom{\rule{0.25em}{0ex}}\text{kg}$ and it has an average specific heat of $\text{0.3349 kJ/kgº}\cdot \text{C}$ . (b) How long would it take to obtain a temperature increase of $\text{2000º}\text{C}$ , which could cause some metals holding the radioactive materials to melt? (The initial rate of temperature increase would be greater than that calculated here because the heat transfer is concentrated in a smaller mass. Later, however, the temperature increase would slow down because the $5×{\text{10}}^{5}\text{-kg}$ steel containment vessel would also begin to heat up.)

Why does earth exert only a tiny downward pull?
hello
Islam
Why is light bright?
an 8.0 capacitor is connected by to the terminals of 60Hz whoes rms voltage is 150v. a.find the capacity reactance and rms to the circuit
thanks so much. i undersooth well
what is physics
is the study of matter in relation to energy
Kintu
a submersible pump is dropped a borehole and hits the level of water at the bottom of the borehole 5 seconds later.determine the level of water in the borehole
what is power?
power P = Work done per second W/ t. It means the more power, the stronger machine
Sphere
e.g. heart Uses 2 W per beat.
Rohit
A spherica, concave shaving mirror has a radius of curvature of 32 cm .what is the magnification of a persons face. when it is 12cm to the left of the vertex of the mirror
did you solve?
Shii
1.75cm
Ridwan
my name is Abu m.konnek I am a student of a electrical engineer and I want you to help me
Abu
the magnification k = f/(f-d) with focus f = R/2 =16 cm; d =12 cm k = 16/4 =4
Sphere
what do we call velocity
Kings
A weather vane is some sort of directional arrow parallel to the ground that may rotate freely in a horizontal plane. A typical weather vane has a large cross-sectional area perpendicular to the direction the arrow is pointing, like a “One Way” street sign. The purpose of the weather vane is to indicate the direction of the wind. As wind blows pa
hi
Godfred
Godfred
If a prism is fully imersed in water then the ray of light will normally dispersed or their is any difference?
the same behavior thru the prism out or in water bud abbot
Ju
If this will experimented with a hollow(vaccum) prism in water then what will be result ?
Anurag
What was the previous far point of a patient who had laser correction that reduced the power of her eye by 7.00 D, producing a normal distant vision power of 50.0 D for her?
What is the far point of a person whose eyes have a relaxed power of 50.5 D?
Jaydie
What is the far point of a person whose eyes have a relaxed power of 50.5 D?
Jaydie
A young woman with normal distant vision has a 10.0% ability to accommodate (that is, increase) the power of her eyes. What is the closest object she can see clearly?
Jaydie
29/20 ? maybes
Ju
In what ways does physics affect the society both positively or negatively
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try to read several books on phy don't just rely one. some authors explain better than other.
Ju
And don't forget to check out YouTube videos on the subject. Videos offer a different visual way to learn easier.
Ju
hope that helps
Ju
I have a exam on 12 february
what is velocity
Jiti
the speed of something in a given direction.
Ju