Friday, August 29, 2014

Quiz #1 Review


2.8, 2.43, 2.75, 2.99,


3.1, 3.49, 3.72, 3.101









 





3b: 3.12-3.21


3.12




3.14



3.15


3.17 









Class Examples: 3.72, 3.81, 3.83, 3.87









Hw 3b: 3.41, 3.47, 3.74, 3.82:




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3.1
7







Class Examples: 3.101, 3.107, 3.111, 3.124, 3.128












HW 3c: 3.106, 3.112, 3.122





Ch3a: Equivalent Systems of Forces on rigid bodies

Yiheng's youtube lectures#10-#16:
 
 Statics Lecture 10: What is moment of a force?  
https://www.youtube.com/watch?v=pSK1h1Aylsk

Statics Lecture 11: Moment calculation scalar formulation  
https://www.youtube.com/watch?v=_xBHygW70tE

Statics Lecture 12: Moment calculation vector formulation  
https://www.youtube.com/watch?v=Lg3P4uIlgeU


Statics Lecture 13: Moment about a specified axis.  
https://www.youtube.com/watch?v=wfhYXm0l6BY


Statics Lecture 14: Principle of moments
https://www.youtube.com/watch?v=i7g2x8dn87Q



Statics Lecture 15: Moment of a couple  
https://www.youtube.com/watch?v=mNBQKPnri3E

Statics Lecture 16: Simplification of a force and moment system  
https://www.youtube.com/watch?v=FDCNEp3TQHg

 

Rigid Bodies vs. Particle





Treatment of a body as a single particle is not always possible.  In general, the size of the body and the specific points of application of the forces must be considered.

Particle Problems:  Forces act through a point



Rigid Body Problems: Have to worry about moments



Different types of moments:


moment of a force about a point
moment of a force about an axis
moment due to a couple

Any system of forces acting on a rigid body can be replaced by an equivalent system consisting of one force acting at a given point and one couple.


Different Types of Forces:



External force - gravity


Internal force:
Tension or compression inside a beam







What is a "moment of a force"?*************

Any force that is applied to a rigid body causes the body to translate or rotate or both.
• The tendency to ROTATE is caused by MOMENTS generated by the force.











In general, a force F generates a moment about any point O which is offset by some distance from the line of action of F.

Moments are Vectors








Review Cross products:
http://en.wikipedia.org/wiki/Cross_product





 3.4 Vector Cross Product


3.5

3.6





3.7


3.8





Chap 3.1-3.8
See example problems 3.1, 3.2, 3.3, and 3.4 in your book
pg 87-89



Class practice problems:
3.4, 3.24









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HW3a: 2.104, 2.107,  3.9, 3.29











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3.9



3.10


3.11







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See example problems 3.5 in text pg 102.

Class examples:  3.37, 3.53





HW 3b: 3.41, 3.47, 3.74, 3.82











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