UNIT 2

Question 1

equilibrium

Answer 1

the resultant force R and the resultant couple M are both zero, and we
have the equilibrium equations
* R= ΣF = 0 M= ΣM=0

Question 2

a mechanical system

Answer 2

a body or group of bodies which can be conceptually
isolated from all other bodies.

representation of the isolated system treated
as a single body.
all forces applied to the system by mechanical
contact with other bodies, which are to be removed.

Question 3

what is a truss

Answer 3

analyze the internal forces acting than are necessary to maintain an equilibrium
configuration.

A framework composed of members joined at their ends to form a rigid structure

beams, channels, angles, bars, and special shapes
which are fastened together at their ends by welding, riveted connections, or large bolts or pins.

Question 4

how to design a truss

Answer 4

first determine the forces in the various member and then select appropriate sizes and structural shapes to withstand the forces.

assume all members to be two-force members.

equilibrium under the action of two forces only.

Question 5

type of trusses

Answer 5

Basic element of a plane
truss is the triangle

Four or more bars pin-jointed to form a polygon of as many sides constitute a nonrigid frame.

By adding a diagonal bar joining A and D or B and C and thereby forming two
triangles.

Question 6

Method of joints:

Answer 6

satisfy the conditions of equilibrium for the forces acting on the connecting pin of each joint.

joints indicated by letters,

designate the force in each
member by the two letters at ends of the member.

tension will always be indicated by an arrow away from the pin,

use equation ∑Fy = 0 and
then found from ∑Fx = 0.

Question 7

Special Conditions: Trusses

Answer 7

When two collinear members are under compression, it is necessary to add a third member to maintain alignment of the two members and prevent buckling.

Question 8

members and joints

Answer 8

2j(joints)=m(members)+3

Question 9

what is it called when there are more than 2 supports

Answer 9

continuous beams

Question 10

what is statically undetermined

Answer 10

no of unknown reactions > = redundant structures

do not have more supporting constraints than are necessary to maintain an equilibrium
configuration.