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UNITS, PHYSICAL QUANTITIES AND VECTORS
1.1.
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IDENTIFY: Convert units from mi to km and from km to ft. SET UP: 1 in. = 2.54 cm, 1 km = 1000 m, 12 in. = 1 ft, 1 mi = 5280 ft.
⎛ 5280 ft ⎞ ⎛ 12 in. ⎞ ⎛ 2.54 cm ⎞ ⎛ 1 m ⎞ ⎛ 1 km ⎞ = 1.61 km EXECUTE: (a) 1.00 mi = (1.00 mi) ⎜ ⎝ 1 mi ⎟⎠ ⎜⎝ 1 ft ⎟⎠ ⎜⎝ 1 in. ⎟⎠ ⎜⎝ 102 cm ⎟⎠ ⎜⎝ 103 m ⎟⎠
1.2.
⎛ 103 m ⎞⎛ 102 cm ⎞ ⎛ 1 in. ⎞⎛ 1 ft ⎞ 3 (b) 1.00 km = (1.00 km) ⎜ ⎟⎜ ⎟ = 3.28 × 10 ft ⎜ 1 km ⎟⎜ ⎟⎜ 1 m ⎟⎟ ⎝⎜ 2.54 cm ⎠⎝ 12 in . ⎠ ⎝ ⎠⎝ ⎠ EVALUATE: A mile is a greater distance than a kilometer. There are 5280 ft in a mile but only 3280 ft in a km. IDENTIFY: Convert volume units from L to in.3. SET UP: 1 L = 1000 cm3. 1 in. = 2.54 cm
⎛ 1000 cm3 ⎞ ⎛ 1 in. ⎞3 3 EXECUTE: 0.473 L × ⎜ ⎟⎟ × ⎜ ⎟ = 28.9 in. . ⎜ 1L 2 54 cm . ⎠ ⎝ ⎠ ⎝ EVALUATE: 1 in.3 is greater than 1 cm3 , so the volume in in.3 is a smaller number than the volume in 1.3.
cm3 , which is 473 cm3. IDENTIFY: We know the speed of light in m/s. t = d/v. Convert 1.00 ft to m and t from s to ns. SET UP: The speed of light is v = 3.00 × 108 m/s. 1 ft = 0.3048 m. 1 s = 109 ns. 0.3048 m EXECUTE: t = = 1.02 × 1029 s = 1.02 ns 3.00 × 108 m/s EVALUATE: In 1.00 s light travels 3.00 × 108 m = 3.00 × 105 km = 1.86 × 105 mi.
1.4.
IDENTIFY: Convert the units from g to kg and from cm3 to m3. SET UP: 1 kg = 1000 g. 1 m = 1000 cm. EXECUTE: 19.3
3
⎛ 1 kg ⎞ ⎛ 100 cm ⎞ kg × × = 1.93 × 104 3 3 ⎜ 1000 g ⎟ ⎜ 1 m ⎟ cm ⎝ m ⎠ ⎝ ⎠ g
EVALUATE: The ratio that converts cm to m is cubed, because we need to convert cm3 to m3. 1.5.
IDENTIFY: Convert volume units from in.3 to L. SET UP: 1 L = 1000 cm3. 1 in. = 2.54 cm. EXECUTE: (327 in.3 ) × (2.54 cm/in.)3 × (1 L/1000 cm3 ) = 5.36 L EVALUATE: The volume is 5360 cm3. 1 cm3 is less than 1 in.3 , so the volume in cm3 is a larger number
than the volume in in.3. 1.6.
IDENTIFY: Convert ft 2 to m 2 and then to hectares. SET UP: 1.00 hectare = 1.00 × 104 m 2 . 1 ft = 0.3048 m.
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1-2
Chapter 1
⎛ 43,600 ft 2 ⎞ ⎛ 0.3048 m ⎞2 ⎛ 1.00 hectare ⎞ EXECUTE: The area is (12.0 acres) ⎜ = 4.86 hectares. ⎟⎟ ⎜ ⎟ ⎜ 4 2⎟ ⎜ ⎝ 1 acre ⎠ ⎝ 1.00 ft ⎠ ⎝ 1.00 × 10 m ⎠ EVALUATE: Since 1 ft = 0.3048 m, 1 ft 2 = (0.3048) 2 m 2 . 1.7.
IDENTIFY: Convert seconds to years. SET UP: 1 billion seconds = 1 × 109 s. 1 day = 24 h. 1 h = 3600 s.
⎛ 1 h ⎞ ⎛ 1 day ⎞ ⎛ 1 y ⎞ = 31.7 y. EXECUTE: 1.00 billion seconds = (1.00 × 109 s) ⎜ ⎝ 3600 s ⎟⎠ ⎜⎝ 24 h ⎟⎠ ⎜⎝ 365 days ⎟⎠ EVALUATE: The conversion 1 y = 3.156 × 107 s assumes 1 y = 365.24 d, which is the average for one 1.8.
1.9.
extra day every four years, in leap years. The problem says instead to assume a 365-day year. IDENTIFY: Apply the given conversion factors. SET UP: 1 furlong = 0.1250 mi and 1 fortnight = 14 days. 1 day = 24 h.
⎛ 0.125 mi ⎞⎛ 1 fortnight ⎞ ⎛ 1 day ⎞ EXECUTE: (180,000 furlongs/fortnight) ⎜ ⎟⎜ ⎟⎜ ⎟ = 67 mi/h ⎝ 1 furlong ⎠⎝ 14 days ⎠ ⎝ 24 h ⎠ EVALUATE: A furlong is less than a mile and a fortnight is many hours, so the speed limit in mph is a much smaller number. IDENTIFY: Convert miles/gallon to km/L. SET UP: 1 mi = 1.609 km. 1 gallon = 3.788 L. ⎛ 1.609 km ⎞⎛ 1 gallon ⎞ EXECUTE: (a) 55.0 miles/gallon = (55.0 miles/gallon) ⎜ ⎟⎜ ⎟ = 23.4 km/L. ⎝ 1 mi ⎠⎝ 3.788 L ⎠ 1500 km 64.1 L = 64.1 L. = 1.4 tanks. 23.4 km/L 45 L/tank EVALUATE: 1 mi/gal = 0.425 km/L. A km is very roughly half a mile and there are roughly 4 liters in a
(b) The volume of gas required is
gallon, so 1 mi/gal ∼ 24 km/L, which is roughly our result. 1.10.
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