91Ó°ÊÓ

Figure 5-22 shows overhead views of four situations in which forces act on a block that lies on a frictionless floor.

The problem is based on the calculation of resultant force. The resultant force is described as the total amount of force acting on the object or body along with the direction of the body. The resultant force is zero when the object is at rest or it is traveling with the same velocity as the object.

Generally, for the block to be stationary the direction of the forces acting on it should be exactly opposite to each other and of equal magnitude else the block will move with a constant velocity in the resultant direction of the applied forces.

In figure 2, the direction of the force ${\text{F}}_{\text{1}}$and ${\text{F}}_{\text{2}}$are opposite with respect to each other hand so by applying equal magnitude of the two forces the block will remain stationary.

In figure 4, the resultant force between the combination of the two forces will always have the direction opposite to one of the three forces ${\text{F}}_{\text{1}}$, ${\text{F}}_{\text{2}}$, and ${\text{F}}_{\text{3}}$and hence by applying the appropriate magnitude of the forces the block will remain stationary

In figure 1, the forces ${\text{F}}_1$and ${\text{F}}_{\text{2}}$are not opposite irrespective of the magnitude of the two forces, the block will move with a constant velocity in the direction of the resultant force.

In figure 3, the direction of the forces ${\text{F}}_{\text{1}}$, ${\text{F}}_{\text{2}}$, and ${\text{F}}_{\text{3}}$or resultant forces between the combination of these forces is not opposite and hence irrespective of the magnitude of the forces applied the block will move with a constant velocity in the direction of the resultant force.