shah (rps587) – HW 13 – Kleinman – (58225)
1
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printout
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have
26
questions.
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before answering.
This HW covers Chs. 18, 19.
001
10.0 points
A water hose 2
.
23 cm in diameter is used to
fill a 26 L bucket.
One liter is equal to 1000 cm
3
.
If it takes 1
.
85 min to fill the bucket, what is
the speed at which the water leaves the hose?
Correct answer: 59
.
9724 cm
/
s.
Explanation:
Let :
r
= 1
.
115 cm
,
V
= 26 L
,
and
t
= 1
.
85 min
.
The crosssectional area of the hose is
A
=
π r
2
=
π
(1
.
115 cm)
2
= 3
.
90571 cm
2
.
According to the data given, the flow rate is
equal to
q
=
V
t
=
26 L
1
.
85 min
min
60 s
10
3
cm
3
L
= 234
.
235 cm
3
/
s
.
Equating this to the product of the velocity
of the water
v
and the crosssectional area of
the hose
A
gives
v A
=
q
. Solving for
v
yields
v
=
q
A
=
234
.
235 cm
3
/
s
3
.
90571 cm
2
=
59
.
9724 cm
/
s
.
002
10.0 points
A 1
.
3 m wide by 2
.
1 m long water bed weighs
1084 N.
Find the pressure that the water bed exerts
on the floor.
Assume that the entire lower
surface of the bed makes contact with the
floor.
Correct answer: 397
.
07 Pa.
Explanation:
Let :
W
= 1084 N
,
w
= 1
.
3 m
,
and
ℓ
= 2
.
1 m
.
P
=
W
A
=
W
w ℓ
=
1084 N
(1
.
3 m) (2
.
1 m)
=
397
.
07 Pa
.
003
10.0 points
Blood of density 604 kg
/
m
3
that is to be ad
ministered to a patient is raised about 1
.
03 m
higher than the level of the patient’s arm.
How much greater is the pressure of the
blood than it would be if the container were
at the same level as the arm? The acceleration
of gravity is 9
.
8 m
/
s
2
.
Correct answer: 6096
.
78 Pa.
Explanation:
Let :
ρ
= 604 kg
/
m
3
,
h
= 1
.
03 m
,
and
g
= 9
.
8 m
/
s
2
.
Δ
P
=
ρ g h
= (604 kg
/
m
3
) (9
.
8 m
/
s
2
) (1
.
03 m)
=
6096
.
78 Pa
.
keywords:
004
(part 1 of 2) 10.0 points
In a machine shop, a hydraulic lift is used to
raise heavy equipment for repairs.
The sys
tem has a small piston with a crosssectional
area of 0
.
045 m
2
and a large piston with a
crosssectional area of 0
.
234 m
2
.
An engine
weighing 3500 N rests on the large piston.
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shah (rps587) – HW 13 – Kleinman – (58225)
2
What force must be applied to the small
piston in order to lift the engine?
Correct answer: 673
.
077 N.
Explanation:
Let :
A
1
= 0
.
045 m
2
,
A
2
= 0
.
234 m
2
,
and
F
2
= 3500 N
.
The pressure is the same, so
F
1
A
1
=
F
2
A
2
F
1
=
A
1
F
2
A
2
=
(0
.
045 m
2
) (3500 N)
0
.
234 m
2
=
673
.
077 N
.
005
(part 2 of 2) 10.0 points
If the engine rises 0
.
266 m, how far does the
smaller piston move?
Correct answer: 1
.
3832 m.
Explanation:
Let :
d
2
= 0
.
266 m
.
A hydraulic lift is effectively 100% efficient, so
W
in
=
W
out
F
1
d
1
=
F
2
d
2
d
1
=
F
2
d
2
F
1
=
(3500 N) (0
.
266 m)
673
.
077 N
=
1
.
3832 m
.
006
10.0 points
A simple Utube that is open at both ends is
partially filled with a heavy liquid of density
1000 kg
/
m
3
.
A liquid of density 410 kg
/
m
3
is
then poured into one arm of the tube, forming
a column 5
.
7 cm in height, as shown.
h
5
.
7 cm
light liquid
410 kg
/
m
3
heavy liquid
1000 kg
/
m
3
What is the difference in the heights of the
two liquid surfaces?
Correct answer: 3
.
363 cm.
Explanation:
Let :
ℓ
= 5
.
7 cm
,
ρ
ℓ
= 410 kg
/
m
3
,
and
ρ
h
= 1000 kg
/
m
3
.
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 Spring '09
 KLIENMAN
 Correct Answer

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