Couple Moment
A couple moment refers to the rotational effect produced by a pair of forces acting in opposite directions but not along the same line. It is a measure of the tendency of the forces to rotate an object around a specific axis. In engineering, understanding and calculating couple moments is crucial for designing and analyzing structures and mechanical systems.
3 Key excerpts on "Couple Moment"
eBook - ePubBasic Engineering Mechanics Explained, Volume 1
Principles and Static Forces
- Gregory Pastoll, Gregory Pastoll(Authors)
- 2019(Publication Date)
- Gregory Pastoll(Publisher)
...The purely twisting effect of a couple can be illustrated by the rotation of a drum-major’s mace, as a result of the opposing forces exerted by finger and thumb. (Naturally, the weight of the mace still has to be supported as well.) The turning effect, or moment, produced by a couple is the product of any one of the forces and the distance between them. In the diagram below, the sum of the moments about the centre-point is: Anticlockwise: (F x d/2) + (F x d/2) Therefore: ΣM o = 2(F x d/2) = F d ⤴ The moment of the couple about either of the points P or Q is also Fd ⤴. Definition of a torque One often hears about torque, as a rotational effect. A torque wrench is a tool that imparts a measurable amount of torque to a nut that is being tightened. Engines are rated in terms of how much torque they can deliver. The units of torque are the same as the units of a force moment, namely Nm. So, what is a ‘torque’, and how does it differ from a force moment? The effects of a torque and a force moment are precisely the same: they are both efforts to impart rotational motion. They differ only in this sense: a force moment arises when a known force acts at a known distance from a rotation axis. A torque, on the other hand, arises when forces of an unspecified magnitude act at an unspecified radius from the rotation axis. For example, consider the way in which an electric motor is made to turn. A current passes through windings in an armature, generating an electro-motive force in each winding. The windings are arranged so that these forces are all in the same rotational direction. The windings are not usually all at the same radius from the rotation axis. But the cumulative force moments from all the windings add up to a total turning effect which we call a torque. Likewise, if you use a screwdriver to drive a wood-screw into a piece of wood, simply by the way you rotate your wrist, you impart a turning effect, called a torque...
eBook - ePub- P.K. Jayasree, K Balan, V Rani(Authors)
- 2021(Publication Date)
- CRC Press(Publisher)
...The resultant moment of a couple is called a torque. A couple consists of two equal forces that are parallel to each other and acting in opposite direction. Referring Figure 4.12, the magnitude of the couple can be computed using Equation 4.9. If F is the magnitude of two forces and d is the moment arm or the perpendicular distance between the forces, FIGURE 4.12 Couple. Magnitude of couple = F d (4.9) 4.4 Statics of Particle: Noncoplanar Concurrent Forces in Space Some forces do not lie in the same plane; however, their line of action may sometimes pass-through a single point. Such forces are called noncoplanar concurrent forces. The magnitude of a force F in space as shown in Figure 4.13 is F = (F x 2 + F y 2 + F z 2) (4.10) Components of a force in space as shown in Figure 4.14 are F x = F cos θ x (4.11a) F y = F cos θ y (4.11b) F z = F cos θ z (4.11c) Their direction cosines. are cos θ x = F x F (4.12a) cos θ y = F y F (4.12b) cos θ z = F z F (4.12c) FIGURE 4.13 Noncoplanar concurrent forces system. FIGURE 4.14 Components of a force in space. 4.4.1 Resultant of Concurrent Force Systems in Space Components of the resultant are R x = ∑ F x (4.13a) R y = ∑ F y (4.13b) R z = ∑ F z (4.13c) Magnitude of the resultant is R = (R x 2 + R y 2 + R z 2) (4.14) 4.4.2 Equilibrium of Concurrent Space...
eBook - ePub- Ken Wyatt, Richard Hough(Authors)
- 2013(Publication Date)
- CRC Press(Publisher)
...In most instances both tendencies are present, and we need a concept to measure the turning effect or rotating effect of a force about a point. The torque or moment of a force about a point is the product of the force and the perpendicular distance from the point to the force (Figure 1.6). The perpendicular distance is called the ‘lever arm’ of the force. Being the product of force and length, moments have the units of Newton-metres, Nm, or kNm, etc. It is most important to note that we may measure the moment of a force about any point we choose ; the point does not have to be the centre of gravity, the fulcrum, the point of support or any such particular point. The moment of a force about a point is simply a measure of the turning effect produced by that force about that point. We shall adopt a convention that clockwise moments are positive, and anti-clockwise moments are negative. WORKSHEET 1.1 1.1 A force of 10 kN is applied at an angle of 30° to the horizontal (Figure 1). (a) Calculate the component of this force in each of the directions AB, CD and EF. (b) Confirm for yourself, by rapid sketches drawn approximately to scale, that the values you have computed seem reasonable. 1.2 Figure 2 shows three concurrent forces acting on a body. (a) Are these forces in equilibrium? (b) If not, what additional force would need to be applied to the body in order to produce equilibrium? FIGURE 1 FIGURE 2 1.3 Figure 3 shows an awning erected at the front of a suburban shop. If we assume that the weight of the awning is concentrated at its mid-point: (a) What is the moment of this weight about the hinged support at A? (b) The force in the steel bar BC will also produce a moment about A...
