Physics for Scientists & Engineers & Modern Physics, 9th Ed

Section 1.4 
Conversion of units
 15. A solid piece of lead has a mass of 23.94 g and a volume 
of 2.10 cm
3
. From these data, calculate the density of 
lead in SI units (kilograms per cubic meter).
 16. An ore loader moves 1 200 tons/h from a mine to the 
surface. Convert this rate to pounds per second, using 
1 ton 5 2 000 lb.
 17. A rectangular building lot has a width of 75.0 ft and 
a length of 125 ft. Determine the area of this lot in 
square meters.
 18. Suppose your hair grows at the rate 1/32 in. per day. 
Find the rate at which it grows in nanometers per sec-
ond. Because the distance between atoms in a mole-
cule is on the order of 0.1 nm, your answer suggests 
how rapidly layers of atoms are assembled in this pro-
tein synthesis.
 19. Why is the following situation impossible? A student’s dor-
mitory room measures 3.8 m by 3.6 m, and its ceiling 
is 2.5 m high. After the student completes his physics 
course, he displays his dedication by completely wall-
papering the walls of the room with the pages from his 
copy of volume 1 (Chapters 1–22) of this textbook. He 
even covers the door and window.
 20. A pyramid has a height of 481 ft, and its base covers an 
area of 13.0 acres (Fig. P1.20). The volume of a pyra-
mid is given by the expression V 5
1
3
Bh, where B is the 
area of the base and h is the height. Find the volume of 
this pyramid in cubic meters. (1 acre 5 43 560 ft
2
)
 21. The pyramid described in Problem 20 contains 
approximately 2 million stone blocks that average 2.50 
tons each. Find the weight of this pyramid in pounds.
W
W
W
W
Figure P1.20 
Problems 20 and 21.
Ad
am
S
yl
ve
st
er
/P
ho
to
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es
ea
rc
her
s,
In
c.

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problems