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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 1437
Problem 7.12
The
300 lb
door is at rest when the man
M
starts pushing it to the
right. If the width and height of the door are both
`D10 ft
, its
center of mass
G
is at its geometric center, and the man pushes at a
height
hD4ft
, determine the horizontal force with which he must
push if he is to move the door
10 ft
to the right in
3
s, and determine
the reactions at the rollers Aand B.
Solution
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.
Solving, we obtain
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Dynamics 2e 1439
Problem 7.13
The portable hydraulic crane with mass
mGD60 kg
is stationary as
it lifts the crate with mass
mCD110 kg
vertically with acceleration
aCD2:5 m=s2
. The mass center of the crate is at
C
and the mass
center of the crane is at
G
. If
dD0:145
m,
`D1:3
m, and
hD
0:27
m, determine the reaction on each of the two front
F
and the two
rear Rwheels.
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.
Computation.
Substituting the kinematic equations into the Newton-Euler equations, the first of the
Newton-Euler equations gives 0D0and the second and third become
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permission of McGraw-Hill, is prohibited.
Dynamics 2e 1441
Problem 7.14
The portable hydraulic crane with mass
mGD60 kg
is stationary as it
lifts the crate with mass
mCD110 kg
vertically with acceleration
aC
.
The mass center of the crate is at
C
and the mass center of the crane
is at
G
. If
dD0:145
m,
`D1:3
m, and
hD0:27
m, determine the
maximum value of the acceleration
aC
, such that no wheel reaction
exceeds
400
N. Assume that the crane is laterally symmetric so that
the loads on the front wheels are equal and the loads on the rear
wheels are equal.
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 neither the crate or crane are rotating or moving in the
x
direction, the
kinematic equations are:
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permission of McGraw-Hill, is prohibited.
Dynamics 2e 1443
Problem 7.15
During takeoff, the thrust from each of the two engines of a Boeing
737 is
TD95 kN
. The mass center of the airplane is located at
G
, the horizontal distance between the main landing gear and
G
is
dD5:15
m, the horizontal distance between the front landing
gear and the main landing gear is
`D11:1
m, and the height of the
mass center above the ground is
hD2:36
m. The mass of the plane
is
mD74;200 kg
, and the thrust from each engine is a distance
ıD1:15 m above the ground.
As the airplane begins its takeoff, the lift
L
from its wings can
be neglected. Determine the normal reaction on the front landing
gear and each of the two wheels of the main landing gear at the start
of takeoff.
Solution
An FBD of the plane at the start of takeoff is shown on the right, where
F
f
is the force on the front landing gear and
Fm
is the force on each
of the two wheels of the main landing gear. We have neglected the lift
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.
1444 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 1445
Problem 7.16
During takeoff, the thrust from each of the two engines of a Boeing
737 is
TD95 kN
. The mass center of the airplane is located at
G
, the horizontal distance between the main landing gear and
G
is
dD5:15
m, the horizontal distance between the front landing
gear and the main landing gear is
`D11:1
m, and the height of the
mass center above the ground is
hD2:36
m. The mass of the plane
is
mD74;200 kg
, and the thrust from each engine is a distance
ıD1:15 m above the ground.
Assuming that the wings are the only surfaces generating lift
during takeoff, determine the lift
L
generated by each wing when
the normal force on the main landing gear is 25% of its initial takeoff
value. The line of action of Lgoes through G.
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permission of McGraw-Hill, is prohibited.
