chen (sbc555) – oldhomework 01 – Turner – (58220)
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001
10.0 points
Suppose
that
you
wish
to
find
out
how
much gasoline is in an underground storage
tank.
You pour in one gallon of gasoline
that contains some halflife radioactive mate
rial that causes a Geiger constant to register
41600 counts per minute above background
radiation.
The next day you remove a gal
lon from the underground tank and measure
its radioactivity to be 100 counts per minute
above background.
How much gasoline is in the tank?
Correct answer: 416 gallons.
Explanation:
After mixing, the gallon you withdraw has
100
41600
=
1
416
of the original radioactive par
ticles in it, so the withdrawn gallon is
1
416
of
the total volume of gasoline in the tank and
there are 416 gallons of gasoline in the storage
tank.
The same method can be used to measure
the volume of blood in creatures, including
humans. Information about blood flow as well
as volume is obtained by injecting radioiso
topes such as chromium51 into the blood
stream.
002
(part 1 of 2) 10.0 points
The mean radius of a planet is 6
.
52
×
10
6
m,
and that of its moon is 1
.
42
×
10
8
cm.
From this data calculate the ratio of the
planet’s surface area to that of its moon.
Correct answer: 21
.
0823.
Explanation:
Let :
r
planet
= 6
.
52
×
10
6
m
and
r
moon
= 1
.
42
×
10
8
cm = 1
.
42
×
10
6
m
.
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 Spring '09
 NUI
 Physics, Work, Neutron, Correct Answer, Observable universe

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