bello (rtb473) – hw14 – Demkov – (59910)
1
This printout should have 40 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
001
10.0 points
Why do ice cubes ±oat?
1.
Ice cubes are less dense than water.
cor
rect
2.
Ice cubes are in a solid state.
3.
Ice cubes are lighter than water.
Explanation:
Ice cubes are less dense than water. IF ice
were more dense than water, it would sink,
and the bottom oF ponds and oceans could be
covered by ice during the winter.
002
10.0 points
When an air bubble rises in water, what hap
pens to its mass, volume, and density?
1.
Volume doesn’t change;
mass and
desnisty increase.
2.
Volume doesn’t change; mass and density
decrease.
3.
Mass doesn’t change; volume increases
and density decreases.
correct
4.
All three are conserved.
5.
Density doesn’t change; mass and volume
decrease.
6.
Density doesn’t change; mass and volume
increase.
7.
Mass doesn’t change; volume decreases
and density increases.
Explanation:
d
=
m
V
The mass will not change (Boyle’s Law).
The bubble’s pressure decreases so its vol
ume increases and the density decreases (same
mass, smaller volume).
003
(part 1 oF 2) 10.0 points
Calculate the ±ow rate oF blood (oF density
1
.
58 g
/
cm
3
) in an aorta with a crosssectional
area oF 2
.
82 cm
2
iF the ±ow speed is 24
.
8 cm
/
s.
Correct answer: 110
.
499 g
/
s.
Explanation:
Let :
ρ
= 1
.
58 g
/
cm
3
,
A
= 2
.
82 cm
2
,
and
v
= 24
.
8 cm
/
s
.
²low Rate =
m
t
=
m
v
d
=
ρ V
v
d
=
ρ A v
= (1
.
58 g
/
cm
3
) (2
.
82 cm
2
) (24
.
8 cm
/
s)
= (1
.
58 g
/
cm
3
) (69
.
936 cm
3
/
s)
= 110
.
499 g
/
s
.
004
(part 2 oF 2) 10.0 points
Assume the aorta branches to Form a large
number oF capillaries with a combined cross
sectional area oF 4480 cm
2
.
What is the ±ow speed in the capillaries?
Correct answer: 0
.
0156107 cm
/
s.
Explanation:
Let :
A
′
= 4480 cm
2
.
²rom the equation oF continuity, we have
v
′
=
A
A
′
v
=
p
2
.
82 cm
2
4480 cm
2
P
(24
.
8 cm
/
s)
= 0
.
0156107 cm
/
s
.
005
10.0 points
The approximate inside diameter oF the aorta
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View Full Documentbello (rtb473) – hw14 – Demkov – (59910)
2
is 1
.
5 cm, and that of a capillary is 1
.
1
×
10
−
6
m. The average Fow speed is about 1
.
0 m/s
in the aorta and 1
.
0 cm/s in the capillaries.
If all the blood in the aorta eventually Fows
through the capillaries, estimate the number
of capillaries in the circulatory system.
Correct answer: 1
.
8595
×
10
10
.
Explanation:
Basic Concepts:
A
c,tot
v
c
=
A
a
v
a
A
c,tot
=
N A
c
A
=
πr
2
Given:
r
a
=
1
.
5 cm
2
= 0
.
75 cm
r
c
=
1
.
1
×
10
−
6
m
2
= 0
.
55
×
10
−
6
m
v
a
= 1
.
0 m
/
s
v
c
= 1
.
0 cm
/
s
Solution:
A
c,tot
=
A
a
v
a
v
c
N
(
π r
2
c
) =
(
π r
2
a
)
v
a
v
c
N
=
r
2
a
v
a
r
2
c
v
c
N
=
(0
.
75 cm)
2
(1 m
/
s)
(5
.
5
×
10
−
7
m)
2
(1 cm
/
s)
p
1 m
100 cm
P
= 1
.
8595
×
10
10
capillaries
006
10.0 points
A water hose 2
.
81 cm in diameter is used to
±ll a 25 L bucket.
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 Spring '07
 Swinney
 mechanics, Correct Answer, Pressure measurement

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