PHYS-1401: College Physics-I
HOMEWORK PROBLEMS
CRN 55178
Khalid Bukhari
HW-1
Chapter 1: INTRODUCTION
PART-A: Hand in your answers in class on scantron on Wednesday 08 September-2010
1.
Suppose two quantities, A and B, have different dimensions. Determine which of the following
arithmetic operations could be physically meaningful.
(a) A + B
(b) B − A
(c) A − B
(d) A/B
(e) AB
2.
A rectangular airstrip measures 32.30 m by 210 m, with the width measured more accurately
than the length. Find the area, taking into account significant figures.
(a) 6.783 0 x 103 m2
(b) 6.783 x 103 m2
(c) 6.78 x 103 m2
If 210 reads as three significant figures
(d) 6.8 x 103 m2
If 210 reads as two significant figures
3
2
(e) 7 x 10 m
3.
Use the rules for significant figures to find the answer to the addition problem
21.4 + 15 + 17.17 + 4.003.
(a) 57.573
(b) 57.57
(c) 57.6
(d) 58
sum = 57.573 rounded to zero places of decimal
(e) 60
4.
A house is advertised as having 1 420 square feet under roof. What is the area of this house in
square meters?
(a) 115 m2
(b) 132 m2
(c) 176 m2
(d) 222 m2
(e) none of these
2
 1.00 m 
A  1.42  102 ft 2 
 1.32  102 m2  132 m2
 3.281 ft 


5.
If an equation is dimensionally correct, does this mean that the equation must be true?
a) Yes
b) No
It may be dimensionally correct, but have some other error
c) Maybe
6.
If an equation is not dimensionally correct, does this mean that the equation can’t be true?
a) Yes
Equation must be dimensionally correct to be true
b) No
c) Maybe
1
PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-1
7.
A rectangular plate has a length of (21.3 ± 0.2) cm and a width of (9.8 ± 0.1) cm. Calculate the
area of the plate, including its uncertainty.
a) 209 cm2 ± 40 cm2
b) 209 cm2 ± 4 cm2
c) 209 cm2 ± 0.4 cm2
d) 209 cm2 ± 0.04 cm2
A  w    21.3  0.2  cm    9.8  0.1 cm 
A   21.3  9.8   21.3  0.1  0.2  9.8   0.2  0.1  cm 2
The first term gives the best value of the area. The second and third terms add to give the uncertainty and the fourth
term is negligible in comparison to the other terms. The area and its uncertainty are found to be
A  209 cm2  4 cm2
8.
a)
b)
c)
d)
The speed of light is about 3.00 x 108 m/s. Convert this figure to miles per hour.
6.71 x 109 mi/h
6.71 x 108 mi/h
6.71 x 107 mi/h
6.71 x 106 mi/h

m   3 600 s   1 km   1 mi 
c   3.00  10 8
 6.71  10 8 mi h
s   1 h   103 m   1.609 km 

9.
An automobile tire is rated to last for 50 000 miles. Estimate the number of revolutions the tire
will make in its lifetime.
a) 106
b) 107
c) 108
d) 109
Let diameter 3 ft, circumference 9 ft. Thus, the total number of revolutions the tire might make is
 50 000 mi   5 280 ft mi   3  10 7 rev, or ~ 10 7 rev
total distance traveled
n 

distance per revolution
9 ft rev
10.
A certain corner of a room is selected as the origin of a rectangular coordinate system. If a fly is
crawling on an adjacent wall at a point having coordinates (2.0, 1.0), where the units are meters,
what is the distance of the fly from the corner of the room?
a) 1.0 m
b) 2.0 m
c) 3.0 m
d) 2.2 m
e) 1.2 m
d 
x 2  y2 =
 2 .0 m  2  1.0 m  2 =
2.2 m
11.
Express the location of the fly in Problem 36 in polar coordinates.
a) r = 3.0 m, θ= 30°
b) r = 2.2 m, θ= 30°
c) r = 2.2 m, θ= 27°
y
1.0 m

 0.50 and
  tan1  0.50   27
x
2 .0 m
The polar coordinates are r = 2.2 m and  = 27 .
tan  
d) r = 3.0 m, θ= 27°
2
PHYS-1401: College Physics-I
CRN 55178
Khalid Bukhari
HW-1
PART-B: Hand in your solutions to the following questions in class, on Wednesday 08 September-2010.
Show the detailed calculations. Write your final answers in the box.
1.
A ladder 9.00m long leans against the side of a building. If the ladder is inclined at an angle of
75.0° to the horizontal, what is the horizontal distance from the bottom of the ladder to the
building?

d  L cos  75.0 
2.
 9.00 m  cos  75.0
 2.33 m
A surveyor measures the distance across a straight river by the following method: Starting
directly across from a tree on the opposite bank, he walks 100 m along the riverbank to establish
a baseline. Then he sights across to the tree. The angle from his baseline to the tree is 35.0°. How
wide is the river?
w
 tan 35.0, or
100 m
w   100 m  tan 35.0   70.0 m
3.
The base of a pyramid covers an area of 13.0 acres (1 acre = 43 560 ft2) and has a height of 481
ft (Fig. P1.26). If the volume of a pyramid is given by the expression V = bh/3, where b is the
area of the base and h is the height, find the volume of this pyramid in cubic meters.
Volume of pyramid 

1
 area of base   height 
3
1
  13.0 acres  43 560 ft 2 acre   481 ft   9.08  10 7 ft 3

3


 2 .832  10  2 m 3 
6
3
 9.08  10 7 ft 3 
  2 .57  10 m
1 ft 3


4.

A firkin is an old British unit of volume equal to 9 gallons. How many cubic meters are there in
6.00 firkins?
 9 gal   3.786 L   103 cm 3   1 m 3 
3
6.00 firkins  6.00 firkins 


  106 cm 3   0.204 m

1
firkin
1
gal
1
L



5.
Newton’s law of universal gravitation is represented by
where F is the gravitational force, M and m are masses, and r is a length. Force has the SI units
kg · m/s2. What are the SI units of the proportionality constant G?
kg m/s2
3