Physics 8 — Friday, November 10, 2017

I HW09 due Monday.

I HW10 due next Friday. Pick up handout today.

I This week, you read Onouye/Kane ch4 (load tracing) & ch5(strength of materials) in Perusall.

I Next week, you’ll read [in Perusall] Onouye/Kane ch6(cross-sectional properties, i.e. centroids & 2nd moment ofarea) and O/K ch7 (simple beams).

I Richard Farley will do most of the talking today.

There’s one problem similar to this (but using metric units) onHW9: Determine the support reactions at A and B.

Maybe Prof. Farley can talk us through some of these?

I line of action

I principle of transmissibility

I moment of a force

I varignon’s theorem

I couple

I moving a force to a parallelline of action by adding acouple

I equilibrium

I colinear forces

I coplanar forces

I concurrent forces

I resultant of several forces

I free-body diagram

I statically indeterminate

I unstable (or unconstrained/ underconstrained)

I reaction force

I types of support conditions

I support reaction

I How to specify wind load?

I Truss bridge whose topforms parabolic arch (likePalmyra-Tacony).

I What is tributary area incase of overhang?

For most of the hour, Prof. Farley showed us his approach tosolving trusses. His handout is here:

http://positron.hep.upenn.edu/p8/files/farley_truss_slides_20171110.pdf

This one is harder than your homework, because the distributedload is non-uniform: Determine the support reactions at A and B.

Here’s another truss problem that you can solve using the Methodof Sections. Find forces in members CE, CF, and DF, withassumed force directions as shown.

I What happens if an assumed force direction is backwards?

I Where should we “section” the truss?

I Then what do we do next?

This is not really a “truss problem,” since we’re not asked to solvefor the internal forces in the truss, but it is an example of a prettytricky equilibrium problem.

Let’s try working through this together in class.

Notice, from the given dimensions: the angle of the incline is thesame as the interior angle at joints A and B of the truss. Alsonotice pin/hinge support at A and roller support at B.

Physics 8 — Friday, November 10, 2017

I HW09 due Monday.

I HW10 due next Friday. Pick up handout today.

I This week, you read Onouye/Kane ch4 (load tracing) & ch5(strength of materials) in Perusall.

I Next week, you’ll read [in Perusall] Onouye/Kane ch6(cross-sectional properties, i.e. centroids & 2nd moment ofarea) and O/K ch7 (simple beams).

I Richard Farley will do most of the talking today.