Examples
Example 1 Answer
How much heat is required to raise the temperature of A kg of water from T1 (in C) to T2 (in C)?
Example 2 Answer
A vehicle weighing B kg is brought to rest by using the brakes, from a speed of S km/hour. How many kilocalories are generated?
Examples 3a, 3b, and 3c Answers
3a
It takes work to shake a can of juice. What happens to the work?
3b
Many heating systems use water as the medium (some radiators, for example). The specific heat of water is relatively large. Why does this make water a good medium for such systems?
Example 4 Answer
Assume that a cooling system in a car holds 16 L of water. How much heat is absorbed by the water if the heat of the water rises from 20 degrees C to 90 degrees C? Note that a liter of water has a mass of 1 kg.
Example 5 Answer
Your task is to melt 16 kg of silver that is at an initial temperature of 20 degrees centigrade. How much heat is required?
Example 6 Answer
Assume that you have water in a metal canteen that is enclosed in a cloth jacket. Why does the water stay cooler if you keep the jacket moist?
Heat Transfer: Conduction, Convection, and Radiation
Example 7 Answer
Some people have become lost in the arctic and have survived by covering themselves with snow. What is the advantage of this?
Example 8 Answer
Assume that you have an aluminum rod that has a diameter of 2.0 cm. One end is kept at 460 degrees C and the other is immersed in water at 22 degrees C. What is the heat conduction rate along the rod?
Example 9 Answer
Calculate how much power is radiated by a tungsten sphere that has an emissivity of 0.35 and a radius of 22 cm. It has a temperature of 25 degrees C.
Sample Multiple-Choice Questions and Answers, Part a
1 The amount of heat necessary
to raise the temperature of 1 gram of water by 1°C is referred to as the
A) calorie.
B) kilocalorie.
C) British thermal unit.
D) joule.
2 The measure of the average
kinetic energy of individual molecules is referred to as
A) internal energy.
B) thermal energy.
C) temperature.
D) heat.
3 A cup of water is scooped up
from a swimming pool of water.
Compare the temperature T and the internal energy U of the water, in both
the cup and the swimming pool.
A) TPool is
greater than TCup, and the U is the same.
B) TPool is
less than TCup, and the U is the same.
C) TPool is
equal to TCup, and UPool is
greater than UCup.
D) TPool is
equal to TCup, and UPool is
less than UCup.
4 An ideal gas at STP is first
compressed until its volume is half the initial volume, and then it is
allowed to expand until its pressure is half the initial pressure.
All of this is done while holding the temperature constant.
If the initial internal energy of the gas is U, the final internal
energy of the gas will be
A) U.
B) U/3.
C) U/2.
D) 2U.
5 An ideal gas with internal
energy U at 200°C is heated to 400°C.
Its internal energy then will be
A) still U.
B) 2 U.
C) 1.4 U.
D) 1.2 U.
6 The reason ocean temperatures
do not vary drastically is that
A) water has a relatively high rate of heat conduction.
B) water is a good radiator.
C) water has a relatively high specific heat.
D) water is a poor heat conductor.
Sample Multiple Choice Questions and Answers, Part b