physics 8 | friday, november 10,...
TRANSCRIPT
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.