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HOMEWORK SET 1
2.22
A car of mass 1775 kg travels with a velocity of 100 km/h. Find the kinetic
energy. How high should it be lifted in the standard gravitational field to have a
potential energy that equals the kinetic energy?
Solution:
Standard kinetic energy of the mass is
KIN = ½ m
V
2
= ½
×
1775 kg
×
⎝
⎜
⎛
⎠
⎟
⎞
100
×
1000
3600
2
m
2
/s
2
=
½
×
1775
×
27.778 Nm = 684 800 J
=
684.8 kJ
Standard potential energy is
P
O
T
=
m
g
h
h = ½ m
V
2
/ mg
=
684 800 Nm
1775 kg
×
9.807 m/s
2
=
39.3 m
2.29
A hydraulic lift has a maximum fluid pressure of 500 kPa. What should the
pistoncylinder diameter be so it can lift a mass of 850 kg?
Solution:
With the piston at rest the static force balance is
F
↑
= P A = F
↓
= mg
A
=
π
r
2
=
π
D
2
/4
PA = P
π
D
2
/4 = mg
⇒
D
2
=
4mg
P
π
D
=
2
mg
P
π
= 2
850 kg
×
9.807 m/s
2
500 kPa
×
π
×
1000 (Pa/kPa)
=
0.146 m
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View Full Document 2.37
A 2.5 m tall steel cylinder has a cross sectional area of 1.5 m
2
. At the bottom with
a height of 0.5 m is liquid water on top of which is a 1 m high layer of gasoline.
The gasoline surface is exposed to atmospheric air at 101 kPa. What is the highest
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This homework help was uploaded on 04/10/2008 for the course ME 235 taught by Professor Borgnakke during the Spring '07 term at University of Michigan.
 Spring '07
 Borgnakke

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