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Quiz Feedback | Introductory Physics I with Laboratory
Feedback — Thermal Energy and Thermal Energy
Transfer
You submitted this quiz on Thu 11 Jul 2013 8:21 AM PDT (UTC -0700). You got a
score of 8.00 out of 11.00. You can attempt again, if you'd like.
Some questions provided by Matter and Interactions (3rd. Ed.), R. Chabay & B. Sherwood.
Copyright (2010, John Wiley & Sons). This material is used by permission of John Wiley &
Sons, Inc.
Question 1
For questions 1 to 3...
170 grams of boiling water (temperature
∘
100 C ,
heat capacity 4.2 J/gram/K) are poured into an
aluminum pan whose mass is 900 grams and initial temperature
∘
26 C
(the heat capacity of
aluminum is 0.9 J/gram/K).
(a) After a short time, what is the temperature of the water?
T final
=?
∘
C
You entered:
60.67
Your Answer
60.67
Score

Total
Explanation
1.00
1.00 / 1.00
Question Explanation
Answer : [57.665,63.735]
Change of thermal energy = W + Q. The change of thermal energy of the water and pan is
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water C water
Al C Al
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Quiz Feedback | Introductory Physics I with Laboratory
mwater C water (T2-100)
+mAl C Al (T2-T1) = W + Q, and W = 0 and Q = 0, assuming that the
water and pan reach thermal equilibrium quickly enough that there is little energy transfer due
to a temperature difference to or from the surroundings. Solve for the unknown final
temperature.
Question 2
(b) What simplifying assumptions did you have to make?
Your Answer
Score
The heat capacities for both water and aluminum hardly
change with temperature in this temperature range.

0.25
Energy transfer between the system (water plus pan) and the
surroundings was negligible during this time.

0.25
The thermal energy of the aluminum doesn't change.

0.25
The thermal energy of the water doesn't change.

0.25
Total
Explanation
1.00 /
1.00
Question Explanation
Answer :
-The heat capacities for both water and aluminum hardly change with temperature in this
temperature range.
-Energy transfer between the system (water plus pan) and the surroundings was negligible
during this time.
Question 3
(c) Next you place the pan on a hot electric stove. While the stove is heating the pan, you use a
beater to stir the water, doing 30763 J of work, and the temperature of the water and pan
increases to
∘
89.1 C .
How much energy transfer due to a temperature difference was there
from the stove into the system consisting of the water plus the pan?
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Quiz Feedback | Introductory Physics I with Laboratory
Q=?J
You entered:
12564.32
Your Answer
12564.32
Score

Total
Explanation
1.00
1.00 / 1.00
Question Explanation
Answer : [11970,13230]
Now the Energy Principle reads like this: mwater C water (T3-T2) +mAl C Al (T3-T2) = W + Q,
where we know everything but Q.
Question 4
A certain motor is capable of doing 4500 joules of work in 10 seconds. What is the power output
of this motor?
Power = ? watts
You entered:
450
Your Answer
450
Score

Total
Explanation
1.00
1.00 / 1.00
Question Explanation
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Answer : 450
Power = J/s watts
Question 5
If you follow a diet of 1820 food calories per day (1820 kilocalories), what is your average power
consumption in watts? (A food or "large" calorie is a unit of energy equal to
3
4.2 ∗ 10
J; a
regular or "small" calorie is equal to 4.2 J.)
Please express your answer in terms of Watt.
Note for comparison that the power consumption in a table lamp is typically about 100 watts.
You entered:
88.47
Your Answer
88.47
Score

Total
Explanation
1.00
1.00 / 1.00
Question Explanation
Answer : [84.075,92.925]
Question 6
How many days of a diet of 1820 large calories are equivalent to the gravitational energy change
from sea level to the top of Mount Everest, 8848 m above sea level? Assume your mass is 70
kg. (The body is not anywhere near 100% efficient in converting chemical energy into change in
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Quiz Feedback | Introductory Physics I with Laboratory
altitude. Also note that this is in addition to your basal metabolism.)
You entered:
0.79
Your Answer
0.79
Score

Total
Explanation
1.00
1.00 / 1.00
Question Explanation
Answer : [0.7543,0.8337]
Question 7
A waterfall is 61 meters high. What is the temperature rise in Kelvins of the water from just
before to just after it hits the rocks at the bottom of the falls, assuming negligible air resistance
during the fall and that the water doesn't rebound but just splats onto the rock?
You entered:
142.3
Your Answer
142.3
Score

Total
Explanation
0.00
0.00 / 1.00
Question Explanation
Answer : [0.1349,0.1491]
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Question 8
540 grams of boiling water (temperature
∘
100 C ,
specific heat capacity 4.2 J/K/gram) are
poured into an aluminum pan whose mass is 910 grams and initial temperature
∘
28 C
(the
specific heat capacity of aluminum is 0.9 J/K/gram).
After a short time, what is the temperature of the water?
Tf
=?
∘
C
You entered:
80.90
Your Answer
80.90
Score

Total
Explanation
1.00
1.00 / 1.00
Question Explanation
Answer : [76.855,84.945]
Apply the Energy Principle to the system consisting of the pan and water: ΔE pan + ΔE water
= 0, where ΔE = mCΔT for the pan and for the water. For the pan ΔT = T f − T i ,pan and
for the water ΔT = T f − T i,water . The only unknown is T f . Solve for T f .
Question 9
For above question, what simplifying assumptions did you have to make?
Your Answer
Assume the specific heat capacity is nearly constant in this
Score

0.25

0.25
Explanation
temperature range.
Assume negligible energy transfer between the surroundings
and the system consisting of the pan plus the water.
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Assume that the water temperature hardly changes.

0.25
Assume that energy diffuses throughout the pan and water so

0.25
that all parts reach the same final temperature.
Total
1.00 /
1.00
Question Explanation
Answer :
-Assume that energy diffuses throughout the pan and water so that all parts reach the same
final temperature.
-Assume the specific heat capacity is nearly constant in this temperature range.
-Assume negligible energy transfer between the surroundings and the system consisting of the
pan plus the water.
Question 10
In a certain time interval, natural gas with energy content of 18000 J was piped into a house
during a winter day. In the same time interval sunshine coming through the windows delivered
3000 J of energy into the house. The temperature of the house didn't change. What was
ΔE thermal
of the house?
ΔE thermal
=?J
You entered:
-21000
Your Answer
-21000
Score

Total
Explanation
0.00
0.00 / 1.00
Question Explanation
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Quiz Feedback | Introductory Physics I with Laboratory
Answer : 0
Question 11
For above question, what was |Q|, the magnitude of the energy transfer between the house and
the outside air?
|Q|
=?J
You entered:
0
Your Answer
0
Score

Total
Explanation
0.00
0.00 / 1.00
Question Explanation
Answer : 21000
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