Basic mechanical engineering 2
- 2. Moment : • The Moment of a force is a measure of its tendency to cause a body to rotate about a specific point or axis. This is different from the tendency for a body to move, or translate, in the direction of the force. In order for a moment to develop, the force must act upon the body in such a manner that the body would begin to twist. This occurs every time a force is applied so that it does not pass through the centroid of the body. A moment is due to a force not having an equal and opposite force directly along it's line of action.
- 3. Elements of a Moment • The magnitude of the moment of a force acting about a point or axis is directly proportinoal to the distance of the force from the point or axis. It is defined as the product of the force (F) and the moment arm (d). The moment arm or lever arm is the perpendicular distance between the line of action of the force and the center of moments • Moment = Force x Distance or M = (F)(d)
- 4. Moments Calculate M on point C : Solve • (100 pounds)(12 in) = 1200 pound-inches • (200 pounds)(0 inches) = 0 pound-inches • 1200 pound-inches + 0 pound- inches = 1200 pound-inches
- 6. Lec#03
- 7. Couple • The moment produced by two equal, opposite, and noncollinear forces is called a couple. Couples have certain unique properties and have important applications in mechanics. Assignment Problem : 57,59
- 8. Resultants • The resultant of a system of forces is the simplest force combination which can replace the original forces without altering the external effect on the rigid body to which the forces are applied. Equilibrium of a body is the condition in which the resultant of all forces acting on the body is zero. This condition is studied in statics. When the resultant of all forces on a body is not zero, the acceleration of the body is obtained by equating the force resultant to the product of the mass and acceleration of the body. This condition is studied in dynamics. Thus, the determination of resultants is basic to both statics and dynamics.
- 9. Resultants • Algebraic Method • Assignments : 77,78,83,85