PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HOMEWORK PROBLEMS Chapter 11:
ENERGY IN THERMAL PROCESSES
HW-11
PART-A: Hand in your answers in class on scantron on Monday 29-November-2010. Write your
name, class (1401) and HW # 11 on the scantron.
1. Convert 3.50 x 103 cal to an equivalent number of joules.
(a) 2.74 X 104 J
(b) 1.47 X 104 J
(c) 3.24 X 104 J
(d) 5.33 X 104 J
2. Convert 7.80 x 105 J to the equivalent number of Calories (1 Cal = 1 000 cal).
(a) 186 Cal
(b) 238 Cal
(c) 325 Cal
(d) 418 Cal (e) 522 Cal
3. How much energy is required to raise the temperature of 5.00 kg of lead from 20.0°C to its
melting point of 327°C?
(a) 4.04 X 105 J
(b) 1.07 X 105 J
(c) 8.15 X 104 J
(d) 2.13 X 104 J
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(e) 1.96 X 10 J
4. If 9.30 X 105 J of energy are transferred to 2.00 kg of ice at 0°C, what is the final temperature
of the system?
(a) 22.4°C
(b) 14.2°C
(c) 31.5°C
(d) 18.0°C
(e) 0°C
5. A wall made of wood 4.00 cm thick has area of 48.0 m2. If the temperature inside is 25°C and
the temperature outside is 14°C, at what rate is thermal energy transported through the wall by
conduction?
(a) 82 W
(b) 210 W
(c) 690 W
(d) 1.3 X 103 W
(e) 2.1 X 103 W
6. A granite ball of radius 2.00 m and emissivity 0.450 is heated to 135°C, whereas the ambient
temperature is 25.0°C. What is the net power radiated from the ball?
(a) 425 W
(b) 3.55 X 104 W
(c) 145 W
(d) 2.01 X 103 W
(e) 2.54 X 104 W
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PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-11
7. How long would it take a 1.00 x 103 W heating element to melt 2.00 kg of ice at −20.0°C,
assuming all the energy is absorbed by the ice?
(a) 4.19 s
(b) 419 s
(c) 555 min (d) 12.5 min
(e) 2.00 h
8. An unknown element of mass 0.250 kg, initially at 95.0°C, is dropped into 0.400 kg of water
at 20.0°C contained in an insulated cup of negligible mass and specific heat. If the equilibrium
temperature is 36.0°C, which of the following is the most likely identity of the substance?
(a) aluminum
(b) beryllium
(c) cadmium (d) iron
(e) gold
9. An amount of energy is added to ice, raising its temperature from −10°C to −5°C. A larger
amount of energy is added to the same mass of water, raising its temperature from 15°C to 20°C.
From these results, what can we conclude?
(a) Overcoming the latent heat of fusion of ice requires an input of energy.
(b) The latent heat of fusion of ice delivers some energy to the system.
(c) The specific heat of ice is less than that of water.
(d) The specific heat of ice is greater than that of water.
(e) More information is needed to draw any conclusion.
10. blank
11. A person shakes a sealed, insulated bottle containing coffee for a few minutes. What is the
change in the temperature of the coffee?
(a) a large decrease (b) a slight decrease (c) no change
(d) a slight increase
(e) a large increase
12. A poker is a stiff, nonflammable rod used to push burning logs around in a fireplace. Suppose
it is to be made of a single material. For best functionality and safety, should the poker be made
from a material with
(a) high specific heat and high thermal conductivity,
(b) low specific heat and low thermal conductivity,
(c) low specific heat and high thermal conductivity,
(d) high specific heat and low thermal conductivity, or
(e) low specific heat and low density?
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PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-11
13. Lead pellets, each of mass 1.00 g, are heated to 200°C. How many pellets must be added to
500 g of water that is initially at 20.0°C to make the equilibrium temperature 25.0°C?
Neglect any energy transfer to or from the container.
a) 367
b) 467
c) 552
d) 321
14. An aluminum cup contains 225 g of water and a 40-g copper stirrer, all at 27°C. A 400-g
sample of silver at an initial temperature of 87°C is placed in the water. The stirrer is used to
stir the mixture until it reaches its final equilibrium temperature of 32°C. Calculate the mass
of the aluminum cup.
a) 80 g
b) 100 g
c) 120 g
d) 210 g
15 A 50-g ice cube at 0°C is heated until 45 g has become water at 100°C and 5.0 g has become
steam at 100°C. How much energy was added to accomplish the transformation?
a) 49 J
b) 58 J
c) 21 J
d) 31 J
16.
A 100-g cube of ice at 0°C is dropped into 1.0 kg of water that was originally at 80°C.
What is the final temperature of the water after the ice has melted?
a) 65 C
b) 74 C
c) 91 C
d) 103 C
17. How much energy is required to change a 40-g ice cube from ice at −10°C to steam at
110°C?
a) 0.08 MJ
b) 1.0 KJ
c) 0.12 MJ
d) 0.22 MJ
18.
A glass windowpane in a home is 0.62 cm thick and has dimensions of 1.0 m X 2.0 m.
On a certain day, the indoor temperature is 25°C and the outdoor temperature is 0°C. What
is the rate at which energy is transferred by heat through the glass
a) 6.1 kW
b) 6.8 kW
c) 13.2 kW
d) 3.4 kW
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