Presentation is loading. Please wait.

# Shawn Kenny, Ph.D., P.Eng. Assistant Professor Faculty of Engineering and Applied Science Memorial University of Newfoundland ENGI.

## Presentation on theme: "Shawn Kenny, Ph.D., P.Eng. Assistant Professor Faculty of Engineering and Applied Science Memorial University of Newfoundland ENGI."— Presentation transcript:

Shawn Kenny, Ph.D., P.Eng. Assistant Professor Faculty of Engineering and Applied Science Memorial University of Newfoundland spkenny@engr.mun.ca ENGI 1313 Mechanics I Lecture 18:Moment of a Force About a Specified Axis

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 2 Mid-Term For This Class  Date:October 18  Time: 830am-945am  Location: to be determined  Material:Up to and including problem set #4 Alternate Exam  Onlyand  Only if there is a compelling reason to miss October 18 th and I must be informed by October 15 th with reason provided  Date:October 22  Time: 700pm-815pm  Location: EN 2007  Material:Up to and including problem set #4

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 3 Mid-Term (cont.) General Comments  All students will be required to take the examination Resources  Tutorial problem sets  Quiz problems  Student societies http://www.engr.mun.ca/~societya/ http://www.socb.ca/sample_finals.html

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 4 Lecture 18 Objective to provide scalar and vector methods for determining the moment of a force about a specified axis

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 5 Moment About a Specified Axis The axis of the moment (Mo) about point O is perpendicular to force (F) and position vector (r) plane What is the component moment about the x-, y- or z-axes? Why is this information important? MxMx MyMy MzMz

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 6 Moment About a Specified Axis (cont.) What is the Moment About Point O?

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 7 Moment About a Specified Axis (cont.) What is the Moment About the X-Axis?  Tending to bend the pipe about O MxMx

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 8 Moment About a Specified Axis (cont.) What is the Moment About the Y-Axis?  Tending to unscrew the pipe about O MyMy

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 9 Moment About a Specified Axis (cont.) L

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 10 Moment About a Specified Axis (cont.) Moment Vector About Point O  Use cross product

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 11 Moment About a Specified Axis (cont.) Moment Vector About Point O

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 12 Moment About a Specified Axis (cont.) Moment Component Projected on Y-axis  Recall dot product

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 13 Triple Scalar Product Generalized Statement  Determine the component moment magnitude (|M a |) on a specified axis due to the moment (M o )

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 14 Triple Scalar Product (cont.) Determine the component moment magnitude (|M a |) on a specified axis due to the moment (M o )

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 15 Triple Scalar Product (cont.)

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 16 Triple Scalar Product (cont.)

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 17 Triple Scalar Product (cont.)

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 18 Triple Scalar Product (cont.)

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 19 Moment Vector on Specified Axis Determine the moment vector (M a ) on a specified axis due to the moment (M o ) r r

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 20 Comprehension Quiz 18-01 The force F is acting along DC. Using the triple product to determine the moment of F about the bar BA, you could use any of the following position vectors except ______.  A) r BC  A) r AD  C) r AC  D) r DB  A) r BD Answer: D Force Line of Action Moment Axis

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 21 Comprehension Quiz 18-02 For finding the moment of the force F about the x-axis, the position vector (r) in the triple scalar product should be ___.  A) r AC  A) r BA  C) r AB  D) r BC Answer: C

ENGI 1313 Statics I – Lecture 18© 2007 S. Kenny, Ph.D., P.Eng. 22 References Hibbeler (2007) http://wps.prenhall.com/esm_hibbeler_eng mech_1

Similar presentations

Ads by Google