King Fahd University of Petroleum

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King Fahd University of Petroleum Minerals

• Mechanical Engineering
• Dynamics ME 201
• BY
• Dr. Meyassar N. Al-Haddad
• Lecture 34

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Chapter 18Planar Kinetics of Rigid BodiesWork
and Energy
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Kinetic Energy
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General
Translation
Rotation
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Rotation
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General Plane Motion (Translation and Rotation)
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Example
K.E. of the Body of Bike and man ( translational
)
K.E of the wheel ( Translational Rotational )
Total K.E. 2 Twheel T BMan
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Example 18-1
mB6 kg mD10 kg mC12 kg No slipping Total K.E
?
Block (Translation)
Disk (Rotation)
Cylinder ( Translation Rotation)
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Problem 18-3
K.E. system ? WABWCD10 Ib WBC20 Ib
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The work of a force
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• Work of a Spring Force

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Force That Do No Work

• Force Perpendicular to the displacement
• Weight
• Normal reaction

Rolling resistance force Fr Fr acts at point
which has zero velocity The point is not
displaced
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Pin Reaction
Pin Reaction Do No work Act on zero velocity and
create no displacement
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The Work of a couple
-Do work only when the body undergoes a
rotation -Translation positive work cancels
the negative work -Rotation
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Example 18-2
m 10 kg M 50 NmP 80N, unstretched 0.5 m
total work ?
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Thank you