Solutions Manual for College Physics 2nd Edition by Paul Peter Urone, Roger Hinrichs

,OpenStax College Physics 2e Student Solutions Manual Chapter 1




CHAPTER 1: INTRODUCTION: THE NATURE
OF SCIENCE AND PHYSICS
1.2 PHYSICAL QUANTITIES AND UNITS

1. The speed limit on some interstate highways is roughly 100 km/h. (a) What is this in
meters per second? (b) How many miles per hour is this?



Solution 100 km 1000 m 1h
(a)    27.77 m/s  27.8 m/s
h 1 km 3600 s
100 km 1 mi
(b)   62 mi/h
h 1.609 km


3. Show that 1.0 m/s  3.6 km/h . Hint: Show the explicit steps involved in converting
1.0 m/s  3.6 km/h .


Solution 1.0 m 1.0 m 3600 s 1 km
    3.6 km/h
s s hr 1000 m


5. Soccer fields vary in size. A large soccer field is 115 m long and 85 m wide. What are its
dimensions in feet and inches? (Assume that 1 meter equals 3.281 feet.)

,OpenStax College Physics 2e Student Solutions Manual Chapter 1



Solution 1 ft
115 m   377.3 ft  377 ft long
0.3048 m
12 in.
377.3 ft   4528 in.  4.53  10 3 in. long
1.0 ft

1 ft
85 m   278.9 ft  2.8  10 2 ft wide
0.3048 m
12 in.
278.9 ft   3346 in.  3.3  10 3 in. wide
1.0 ft


7. Mount Everest, at 29,028 feet, is the tallest mountain on the Earth. What is its
height in kilometers? (Assume that 1 kilometer equals 3,281 feet.)



Solution 1 km
29,028 ft   8.847 km
3281 ft


9. Tectonic plates are large segments of the Earth’s crust that move slowly. Suppose
that one such plate has an average speed of 4.0 cm/year. (a) What distance does it
move in 1.0 s at this speed? (b) What is its speed in kilometers per million years?



Solution 4.0 cm  1m 1y 1d 1h
(a) 
 y  1s

     1.3  10 -9 m
  100 cm 365.25 d 24.0 h 3600 s

4.0 cm 1m 1 km 10 6 y
(b)     40 km/My
y 100 cm 1000 m 1 My



1.3 ACCURACY, PRECISION, AND SIGNIFICANT FIGURES

11. Suppose that your bathroom scale reads your mass as 65 kg with a 3% uncertainty.
What is the uncertainty in your mass (in kilograms)?

, OpenStax College Physics 2e Student Solutions Manual Chapter 1



Solution 3%
äm  65 kg  2 kg
100%


13. (a) A car speedometer has a 5.0% uncertainty. What is the range of possible speeds
when it reads 90 km/h ? (b) Convert this range to miles per hour.
(1 km  0.6214 mi)


Solution 5.0%
(a) äv   90.0 km/h  4.5 km/h
100%
Thus, the range  90.0  5 km/h  85 to 95 km/h.

(b) 85.5 km  0.6214 mi  53.1 mi/h ; 94.5 km  0.6214 mi  58.7 mi/h
h 1 km 1h 1 km

So the range is 53.1 to 58.7 mi/h.



15. (a) Suppose that a person has an average heart rate of 72.0 beats/min. How many
beats do they have in 2.0 y? (b) In 2.00 y? (c) In 2.000 y?



Solution 72.0 beats 60.0 min 24.0 h 365.25 d
    2.0 y  7.5738  10 7 beats
1 min 1.00 h 1.00 d 1.00 y

(a) 7.6  10 7 beats (limited by 2.0 y)

(b) 7.57  10 7 beats (limited by 2.00 y)

(c) 7.57  10 7 beats (limited by 72.0 beats/min)



17. State how many significant figures are proper in the results of the following
calculations: (a) 106.7 98.2/ 46.2101.01 (b) 18.7  (c) 1.60  10 19 3712.
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