Torque

Torque, moment, or moment of force is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist to an object. Torque is the result of a cross between a position vector r with a force F.

example:

Calculate the force required to produce 20 Nm torque at an angle of 50º from along a 300 cm rod?

From the question, it is clear that
F = 200N, r = 20 cm = 0.2 m , θ = 90º
τ = rFsinθθ
τ = 0.2 × 200 × sin90
τ = 0.2 × 200 × 1=40 Nm

Couple

Is the force couples of the same amount and in opposite directions. Review a rod by force as in the image below. We can not replace the two styles with a style that will give the same effect to both styles.

Two forces equal and opposite directions but has a different fishing spot called coupling.

Number of these two forces is equal to zero, but the two styles cause the rotation. The torque generated by these two forces to the point O is:

τ = FX2 – FX1 = F (x2 – x1) = Fd

F1 will cause the rod rotates clockwise while F2 causes the rod to rotate anticlockwise.

Equilibrium

Take a board and place it on top of a pile of bricks. Then give the same force on both sides of the board in the opposite direction. What happened? Now we change the layout style. Press the board downward on one side and push the boards on the other hand try to part the board on a pile of bricks is not shifted. What happened? Scheme we do like in the picture below.

a) board by 2 the same force F1 = F2, the second line style
b) Board by two the same style but not in line, ΣF = 0, but the board rotates.

From the above we see a picture if it provides two styles equal but opposite directions on objects will not shift or will not do the translation, because the total force is zero. Objects will be silent. Can we say that the total force is zero the object is in equilibrium? Figure b above shows two opposite and equal force is large but has a different style lines, turns moving objects with rotational movement. So that objects do not rotate the torque on an object must be equal to zero. Now we can deduce the object is in equilibrium if:

Total force = 0 → F = 0

Total torque = 0 → τ = 0

So the equilibrium condition is the total force is zero and the total torque is equal to zero. If the object at first silent, then we give the force and torque equilibrium, then the object will remain stationary or static equilibrium occurs.