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Kinematic Equations.
Since the system is translating with the trolley, there is no rotation and the
y
components of acceleration are zero, which implies
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
Dynamics 2e 1427
Problem 7.6
The uniform slender bar
AB
has a weight
WAB D150 lb
while the
crate’s weight is
WCD500 lb
. The bar
AB
is rigidly attached to the
cage containing the crate. Neglect the mass of the cage, and assume
that the mass of the crate is uniformly distributed. Furthermore, let
LD8:5 ft, dD2:5 ft, hD4ft, and wD6ft.
If the bar-crate system is translating with the trolley so that
D26ı, determine the acceleration a0of the trolley.
2CWAB
2sin DID˛CCIG˛AB
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
Kinematic Equations.
Since the system is translating with the trolley, there is no rotation and the
y
components of acceleration are zero, which implies
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
Dynamics 2e 1429
Problem 7.7
A person is pushing a lawnmower of mass
mD38 kg
and with
hD0:75
m,
dD0:25
m,
`AD0:28
m, and
`BD0:36
m. Assuming
that the force exerted on the lawnmower by the person is completely
horizontal and that the mass center of the lawnmower is at
G
, and
neglecting the rotational inertia of the wheels, determine the minimum
value of this force that causes the rear wheels (labeled
A
) to lift off
the ground. In addition, determine the corresponding acceleration of
the mower.
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permission of McGraw-Hill, is prohibited.
Problem 7.8
The mower is self-propelled through its rear wheels. If a person were
to apply a purely horizontal force, would this force help or hinder
the rear wheels’ contribution to the forward motion of the mower?
That is, would the rear wheels slip less easily or more easily?
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
Dynamics 2e 1431
Problem 7.9
The stationary wheel loader is lifting the load at
B
vertically
with acceleration
a0D10 ft=s2
. If the weight of the load
B
is
10;000 lb
, the weight of the wheel loader is
33;000 lb
,
`D118 in:
,
hD90 in:
, and
dD27 in:
, determine the reactions on each of its
four wheels if the wheel loader is laterally symmetric. In addition,
compute the static load on each of the four wheels (i.e., with
a0D0
) and compare it with the corresponding dynamic load.
The center of mass of the wheel loader is at A.
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permission of McGraw-Hill, is prohibited.
1432 Solutions Manual
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permission of McGraw-Hill, is prohibited.
Dynamics 2e 1433
Problem 7.10
The stationary wheel loader is lifting the load at
B
vertically with
acceleration
a0
. If the weight of the load
B
is
10;000 lb
, the
weight of the wheel loader is
33;000 lb
,
`D118 in:
,
hD90 in:
,
and
dD27 in:
, determine the largest value of
a0
for which the
reaction on each of the rear wheels does not drop below
1000 lb
.
The center of mass of the wheel loader is at A.
FrD1000 lb:
Kinematic Equations.
Since neither the wheel loader nor the crate rotate, all angular accelerations are
0D0; (1)
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permission of McGraw-Hill, is prohibited.
1434 Solutions Manual
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
Dynamics 2e 1435
Problem 7.11
The door is at rest when the man
M
starts pushing it to the right
with a constant horizontal force of
40 lb
. If the weight of the door
is
300 lb
, its width and height are both
`D10 ft
, its center of
mass
G
is at its geometric center, and the man pushes at a height
hD4ft
, determine the speed of the door after it has moved
10 ft
and determine the reactions at the rollers Aand B.
2hCNB
2NA
2DIG˛d;
where
Wd
is the weight of the door and
˛d
is its angular accelera-
tion.
Force Laws. All forces are accounted for on the FBD.
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