Transcript File

Ch 17 Notes – Part 1

Mass Moment of Inertia

• I =  r^2 dm, over m Engineering Mechanics: Dynamics, Thirteenth Edition R. C. Hibbeler Copyright ©2013 by Pearson Education, Inc.

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Ch 17 Notes – Part 1

Mass Moment of Inertia

• • • I =  r^2  dV, over V I =  r^2 dV, over V, constant rho Engineering Mechanics: Dynamics, Thirteenth Edition R. C. Hibbeler Copyright ©2013 by Pearson Education, Inc.

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Ch 17 Notes – Part 1

Mass Moment of Inertia

To evaluate, use either the shell method or the disk method For shell: dV = (2  y)(z)dy Engineering Mechanics: Dynamics, Thirteenth Edition R. C. Hibbeler Copyright ©2013 by Pearson Education, Inc.

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Ch 17 Notes – Part 1

Mass Moment of Inertia

To evaluate, use either the shell method or the disk method For disk: dV = (  y) 2 dz Here, we have to find (d Iz) first and then integrate that Engineering Mechanics: Dynamics, Thirteenth Edition R. C. Hibbeler Copyright ©2013 by Pearson Education, Inc.

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Example 17.1

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Example 17.1 (continued)

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Example 17.2

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Example 17.2 (continued)

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Ch 17 Notes – Part 1

• •

Parallel Axis Theorem

If the moment of inertia about an axis passing through the mass center of a body is known, we can find the moment of inertia of that body about any other parallel axis I z + I G + md 2 Engineering Mechanics: Dynamics, Thirteenth Edition R. C. Hibbeler Copyright ©2013 by Pearson Education, Inc.

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Ch 17 Notes – Part 1

Radius of Gyration

The radius of gyration, k, is sometimes given. Its units are in length I = mk 2 k = sqrt(I/m) Engineering Mechanics: Dynamics, Thirteenth Edition R. C. Hibbeler Copyright ©2013 by Pearson Education, Inc.

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Ch 17 Notes – Part 1

Composite Bodies

Sometimes you can break a complex body up into simple shapes. Find their moments of inertia and add them algebraically.

Use the parallel axis theorem to find their moments of inertia about a common axis.

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Example 17.3

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Example 17.3 (continued)

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Example 17.3 (continued)

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Example 17.4

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Example 17.4 (continued)

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Example 17.4 (continued)

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Ch 17 Notes – Part 1

Planar Kinetic Equations of Motion

F

F

x = m

a

G = m

a

Gx 

F

y  M G  M P = m

a

Gy = I G  =  (

M

k ) P Engineering Mechanics: Dynamics, Thirteenth Edition R. C. Hibbeler Copyright ©2013 by Pearson Education, Inc.

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Ch 17 Notes – Part 1

Equations of Motion: Translation

Rectilinear: 

F

x 

F

y  M G = m( = 0

a

G ) = m(

a

G ) y x Engineering Mechanics: Dynamics, Thirteenth Edition R. C. Hibbeler Copyright ©2013 by Pearson Education, Inc.

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Ch 17 Notes – Part 1

Equations of Motion: Translation

Curvilinear: 

F

n 

Ft

 M G = m( = 0

a

G )n = m(

a

G )t Engineering Mechanics: Dynamics, Thirteenth Edition R. C. Hibbeler Copyright ©2013 by Pearson Education, Inc.

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Example 17.5

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Example 17.5 (continued)

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Example 17.5 (continued)

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Example 17.6

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Example 17.6 (continued)

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Example 17.7

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Example 17.7 (continued)

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Example 17.7 (continued)

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Example 17.8

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Example 17.8 (continued)

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