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Ristinen, Kraushaar, Brack Energy and the Environment Chapt 1 Solutions
Chapter1: EnergyFundamentals
Odd-numbered problems
•Problem 1.3 : Cart on a horizontal surface
Given:F= 10lbandd= 10ft
F×d=W 10lb×10ft= 100ft∙lbs 100ft∙lbs×1.36 j ft∙lb = 136joules
•Problem 1.7 : Tons of coal per person
From Table 1.1:98QBtu/yrused in U.S.
U.S. population approximately300×10 6 people.
98×10
15 Btu× 1ton coal
2.7×10
7 Btu
= 3.6×10
9 tons
Then:
3.6×10
9 tons
300×10
6 people = 12 tons yr∙person , approximately.
•Problem 1.11 : Windmill heats water
40gallons×0.1337 ft 3 gal
×62.4
lb ft 3 = 334lb 334lb×1 Btu lb∙°F ×50°F= 16,700Btuneeded 16,700Btu× 1,055j Btu
= 17.6×10
6 jneeded
1400W= 1400
j sec
17.6×10
6 j 1400j/s = 12,600seconds= 210minutes= 3.5hours 1 (Energy and the Environment, 3e Robert Ristinen, Jack Kraushaar, Jeffrey Brack) (Solution Manaul) 1 / 3
Ristinen, Kraushaar, Brack Energy and the Environment Chapt 1 S olutions Multiple choice problems
•Problem 1.1 : Product with exponentials
Answer: f)
(5×6×7)×10
(5+6+7)
= 210×10
18
= 2.1×10
20
•Problem 1.3: Mass on string
Answer: c)
Initially:P.E.=mgh (see page 113)
= 5kg×9.8 m s 2 ×2m = 98kg m 2 s 2 = 98Joules
•Problem 1.5 : U.S. consumption vs. India
Answer: d)
From Fig. 1.3:
50 4
= 12.5
•Problem 1.7 : Average personal power
Answer: b)
3000C= 3×10
6 cal 3×10 6 cal day
×4.184
j cal × 1day 24hours × 1hour 3600sec = 145 j sec = 145watts
•Problem 1.9 : Fossil fuel percentage of energy use
Answer: c)
From Table 1.1:18.5 + 27.3 + 36.1 = 81.9
2 2 / 3
Ristinen, Kraushaar, Brack Energy and the Environment Chapt 1 S olutions
•Problem 1.11 : Energy in a pound
Answer: b)
1lb= 0.454kg mc 2
= 0.454×(3×10
8 ) 2
= 4.1×10
16
•Problem 1.13 : Math
Answer: c)
4.8×3.6
2.8 ×10
9+5−10
= 6.2×10
4
- / 3
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