Test: Two And Three Force Members - Civil Engineering (CE) MCQ

The definition of the two force member only defines that the forces are being acted on the two points on the body. So does is the definition of the three forces members. The points of action of the three forces are three.

The summation of the forces needs to be zero. So does the summation of the moments need to zero. But talking about the angles, they not needed to zero. But the forces which are acting at particular angles, must needed to be equal to zero. The basic need of the forces to make the body in equilibrium.

The force members doesn’t defines whether the moment will be applied or not. They are basically the forces only. Thus if there is a force applied on the body, there will be a moment produced by them. If not then probably the forces might be collinear.

The influence of the moment on the body is determined by the number of the forces acting on the body. It depend on the magnitude of the force. It also depend whether the forces are collinear or not. Thus the number of forces are not the only parameter for the determination of the moment.

Never judge the application of the moment of the force applied on the body by the number of the forces being acted on the body. What is two of the forces becomes collinear and are having a zero distance from the axis of rotation. Thus the three and two force member apply moments according to the situation, whether the distance is zero or not.

Simply, for the equilibrium the net force must be zero. That is the forces must be collinear if equilibrium is to be established. And they must be in the opposite directions. They also must be of same magnitude, cancelling each other.

The summation of the forces needs to be zero. So does the summation of the moments need to zero. But talking about the angles, they not needed to zero. But the forces which are acting at particular angles, must needed to be equal to zero. The basic need of the forces to make the body in equilibrium.

The moment equilibrium for the three force members is satisfies only when the three forces are concurrent. That is the forces form a parallel system. That is the net force on the three axis turns out to be zero. This will only happen if the forces are in the same plane.

The forces in the three force system is not always in the equilibrium. The equilibrium is established when the forces cancels out each other. Also when the net moment is zero. Then only the equilibrium is established in the three force system.

The summation of the forces needs to be zero. So does the summation of the moments need to zero. But talking about the angles, they not needed to zero. But the forces which are acting at particular angles, must needed to be equal to zero. The basic need of the forces to make the body in equilibrium.

Force component in the direction parallel to the AB is given by unit vector 0.286i + 0.857j + 0.429k. Now (300j).(0.286i + 0.857j + 0.429k) = 257.1N. Just try to resolve the force into it’s particular components.

The forces need to be collinear. If they are not so then the equilibrium is not possible. If they are parallel too, then it is assumed that they are meeting in the infinity. And hence the equilibrium is established between the forces. Thus the forces must be collinear.

The summation of the forces needs to be zero. So does the summation of the moments need to zero. But talking about the angles, they not needed to zero. But the forces which are acting at particular angles, must needed to be equal to zero. The basic need of the forces to make the body in equilibrium.

 As the dot product of only the same Cartesian component is unity, i.e. i.i = 1 and j.j =1, rest all remaining dot product will give 0(i.j = 0 and j.k = 0). Cross product of the same plane vectors always give zero. And dot product of the same plane vector gives a scalar quantity.

Even if the forces components cancels each other than the body is said to be in equilibrium. Also it should satisfy whether the moments caused by the forces are equal to zero or not. This means if the moment caused and the net force is zero the body is in equilibrium.