Title: Engineering Mechanics Lecture 3
1Engineering MechanicsLecture 3
2Tendency of Force to Rotate a Body
- Two effects of force
- Move a body in the direction of its application
- Rotate a body around an axis.
3Moment Arm
Tendency of the force to rotate a body Is
proportional to F and d
d perpendicular distance from the axis to the
line of force action
4Right-Hand Rule
Moment in the direction of thumb
Fingers curl in the direction of the tendency to
rotate
5Sign of Moment (2D Convention)
Plus sign () counter clockwise Minus sign (-)
clockwise
6Many-Particle Interactions
For an N particles system, in equilibrium
3
F3
f32
f23
f31
2
f13
f21
f12
F1
1
7Many-Particle Interactions
Newtons 1st law
For an N particles system, in equilibrium
Can you prove
?
Need Newtons 3rd law
Therefore
8Many-Particle System
For a N-particle system, in equilibrium