SolvedProblems Lec1 Sol
Solved Problems : Doing Physics
1. The power output of a typical large power plant is 1000 megawatts (MW). Express this result in (a) W, (b) kW, and (c) GW.
a)
1000 MW = 103 × 106 W = 109 W
b)
1000 MW = 103 × 106 W = 106 kW
c)
1000 MW = 103 × 106 W = 1 GW
2. A car is moving at 35.0 mi/h. Express its speed in (a) m/s and (b) ft/s.
a)
35 mi/h =
35 × 1.609 × 103
= 15.6 m/s
3600
b)
35 mi/h =
35 × 1.609 × 103 × 102
= 51.3 f t/s
2.54 × 12 × 3600
3. Add 3.63105 m and 2.13103 km .
3.63105 + 2.13103 × 103 = 3.63105 + 2131.03 = 2134.66 m
4. Add 5.131022 cm and 6.83103 mm, and multiply the result by 1.83104 N (N is the SI unit of force).
5.131022 cm = 5.131022 × 10−2 m = 51.31022 × 10−3 m
Adding first the two distances,
. 6.83103 mm = 6.83103 × 10−3 m
.
51.31022 × 10−3 + 6.83103 × 10−3 = 58.14125 × 10−3 m
Now we multiply by the force term,
58.14125 × 10−3 × 1.83104 = 0.106459 N.m
5. Youre driving into Canada and trying to decide whether to fill your gas tank before or after crossing the border. Gas in the United States costs 2.97 $/gallon, in Canada its 94 ¢/L, and the
Canadian dollar is worth 87 ¢ in U.S. currency. Where should you fill up? .
Converting the Canadian cost gives,
0.94 Canadian Dollar/L = 0.94 × 3.785 × 0.87 = 3.09 American Dollar/gal
This is 12 ¢more than the cost in the U.S., so it would be better to buy the gas before crossing the border. 6. Caf´ e Milagro sells coffee online. A half-kilogram bag of coffee costs 8.95 $, excluding shipping. If you order six bags, the shipping costs 6.90 $. Whats the cost per bag when you include shipping? The total purchase is 6 bags plus shipping,
6(8.95 $) + 6.90 $ = 60.60 $
Dividing by the number of bags gives 10.10 $ per bag.
7. Express the following with appropriate units and significant figures: (a) 1.0 m plus 1 mm,
(b) 1.0 m times 1 mm, (c) 1.0 m minus 999 mm, (d) 1.0 m divided by 999 mm.
a) To the least-precise decimal place, we have
1.0 m + 1 × 10−3 m = 1.0 m
b) The least-precise factor, 1 m, has one
1. The power output of a typical large power plant is 1000 megawatts (MW). Express this result in (a) W, (b) kW, and (c) GW.
a)
1000 MW = 103 × 106 W = 109 W
b)
1000 MW = 103 × 106 W = 106 kW
c)
1000 MW = 103 × 106 W = 1 GW
2. A car is moving at 35.0 mi/h. Express its speed in (a) m/s and (b) ft/s.
a)
35 mi/h =
35 × 1.609 × 103
= 15.6 m/s
3600
b)
35 mi/h =
35 × 1.609 × 103 × 102
= 51.3 f t/s
2.54 × 12 × 3600
3. Add 3.63105 m and 2.13103 km .
3.63105 + 2.13103 × 103 = 3.63105 + 2131.03 = 2134.66 m
4. Add 5.131022 cm and 6.83103 mm, and multiply the result by 1.83104 N (N is the SI unit of force).
5.131022 cm = 5.131022 × 10−2 m = 51.31022 × 10−3 m
Adding first the two distances,
. 6.83103 mm = 6.83103 × 10−3 m
.
51.31022 × 10−3 + 6.83103 × 10−3 = 58.14125 × 10−3 m
Now we multiply by the force term,
58.14125 × 10−3 × 1.83104 = 0.106459 N.m
5. Youre driving into Canada and trying to decide whether to fill your gas tank before or after crossing the border. Gas in the United States costs 2.97 $/gallon, in Canada its 94 ¢/L, and the
Canadian dollar is worth 87 ¢ in U.S. currency. Where should you fill up? .
Converting the Canadian cost gives,
0.94 Canadian Dollar/L = 0.94 × 3.785 × 0.87 = 3.09 American Dollar/gal
This is 12 ¢more than the cost in the U.S., so it would be better to buy the gas before crossing the border. 6. Caf´ e Milagro sells coffee online. A half-kilogram bag of coffee costs 8.95 $, excluding shipping. If you order six bags, the shipping costs 6.90 $. Whats the cost per bag when you include shipping? The total purchase is 6 bags plus shipping,
6(8.95 $) + 6.90 $ = 60.60 $
Dividing by the number of bags gives 10.10 $ per bag.
7. Express the following with appropriate units and significant figures: (a) 1.0 m plus 1 mm,
(b) 1.0 m times 1 mm, (c) 1.0 m minus 999 mm, (d) 1.0 m divided by 999 mm.
a) To the least-precise decimal place, we have
1.0 m + 1 × 10−3 m = 1.0 m
b) The least-precise factor, 1 m, has one