e14 - applied mechanics: statics
TRANSCRIPT
1mon/wed/fri, 12:50-2:05pm, 370-370
e14 - applied mechanics: statics
2syllabus
e14 - applied mechanics: statics
fifthhomework
due
38.1 characteristics of dry friction
• the heat generated by theabrasive action of friction canbe noticed when using thisdrinder to sharpen a metalblade• friction is a force thatrisists the movement of twocontacting surfaces relativeto one another• friction always acts tan-gent to the surface and is di-rected opposite to a possiblemotion
from friction to heat
4
theory of dry friction
8.1 characteristics of dry friction
8.2 problems involving dry friction
slipping & tipping
pushing on the uniform crate of weight W sitting on a rough surface. if themagnitude P is small, the crate will remain in equilibrium and not move(left FBD). as P increases, the crate will either be on the verge of slipping,F = µs · M, or, if the surface is very rough with large µs, the resultant forcemoves towards the corner and beyond, x>b/2, and the crate will tip over.tipping also depends on the height h of the force P.
68.2 problems involving dry friction
example 8.1
78.2 problems involving dry friction
example 8.1
88.2 problems involving dry friction
example 8.3
98.2 problems involving dry friction
example 8.3
109. center of gravity and centroid
• to discuss the concept of thecenter of gravity, center ofmass, and centroid• to show how to determinethe center of gravity and cen-troid for a system of par-ticles• to show how to determinethe center of gravity and cen-troid for composite bodies
today‘s objectives
119.1 center of gravity/mass and centroid
location of the center of gravity from sum of all forces andmoments of resultant
center of a collection of particles
x = ! x dW ! dW
y = ! y dW ! dW
z = ! z dW ! dW
129.2 composite bodies
the center of gravity of thiswater tank can be determinedby dividing it into compositeparts
divide the structure!
x = ! x W ! W
y = ! y W ! W
z = ! z W ! W
I
II
III
139.2 composite bodies
example 9.10
149.2 composite bodies
example 9.10
159.2 composite bodies
example 9.11
169.2 composite bodies
example 9.11