Equipment Setup - 3B SCIENTIFIC 1000694 Manual Del Usuario

single plane is defined as that force which, acting
alone in the same plane, would have the same
effect as the combination of the two forces. A
force of equal magnitude to the resultant but
acting in the opposite direction therefore main-
tains the body in equilibrium. The resultant can
be obtained by analysis or by graphical means
using various laws (parallelogram of forces, tri-
angle of forces, polygon of forces).
A parallelogram of forces represents two forces
acting simultaneously on a body as two adjacent
sides of a parallelogram. The magnitude and
direction of their resultant is then given by the
diagonal originating from the same point.
This theorem can be expressed mathematically
as follows: When two forces A
a body with an angle θ between them, the resul-
r
tant R is given by:
2
= +
R A
If α is the angle between the resultant and force
r
then:
A
α =
tan
With the law of the triangle of forces, two forces
acting simultaneously on a body are represented
in terms of magnitude and direction by two follow-
ing sides of a triangle. The magnitude and direc-
tion of the resultant is then given by following the
third side of the triangle in the opposite direction.
From this it can be determined that a body is in
equilibrium if three forces are acting upon it,
r r
and B acting on
2
+ θ
2 cos
B AB
θ
sin
B
+ θ
cos
A B
which can be represented by the three sides of a
triangle.
If more than two forces act on a body at once, the
law of the polygon of forces is used. This repre-
sents several forces acting at the same point as
following sides of a polygon where one side re-
mains open. As for the triangle, following the side
that closes the polygon in the opposite direction
gives the resultant force.
Therefore a body is in equilibrium when several
forces act upon it that can be represented as a
closed polygon. The vector sum of the individual
forces is equal to zero and so is the resultant
force. On closer observation, this law can be
seen to be a simple extension of the law of the
triangle of forces. The force table is suitable for
demonstrating vector addition and equilibrium of
forces and for confirming the graphic and analyti-
cal methods. The equilibrium between two or
three forces can be demonstrated and the magni-
tude and direction of each force easily deter-
mined.
4. Operation

4.1 Equipment Setup

• Place the base on an even surface.
• Screw the centre rod vertically into the base.
2