Forces

FORCEAn action exerted on an object

which may change the object’s state of rest, its shape or motion is called force.

The SI unit of force is the Newton and it is denoted by N.

1 N = 1 kg.1 m/s2

Forces can act through contact or at a distanceIf you pull on a spring, the spring

stretches. If you pull on a wagon, the wagon moves. When a football is caught, its motion is stopped. These pushes and pulls are examples of contact forces.

Another class of force is called field force that does not involve physical contact between two objects.

Force is a vector

Because the effect of a force depends on both magnitude and direction, force is a vector quantity.

Net ForceIf more than one force acts

simultaneously on the same object, net force is the one that determines motion of the object.

Free-body diagramA free-body diagram is used to

analyze only the forces affecting the motion of a single object.

Free-body diagrams are constructed and analyzed just like other vector diagrams.