1. Forces

2. FORCE
 An action exerted on an object which
may change the object’s state of rest,
its shape or motion is called force.

3.  The SI unit of force is the Newton and
it is denoted by N.
 1 N = 1 kg.1 m/s2

4. Forces can act through
contact or at a distance
 If 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.

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

6. Net Force
 If more than one force acts
simultaneously on the same object, net
force is the one that determines motion
of the object.

7. Free-body diagram
 A 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.