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Translational Equilibrium |
| When every part of a
system travels with the same speed in the same fixed direction, we have translational
motion, as compared to rotational motion, where the speeds are different and the direction
changes from moment to moment. Translational equilibrium corresponds
to straight-line motion along a fixed direction at a constant speed, and in this chapter,
taken as zero. In this chapter, we will only
deal with coplanar systems, where all the forces acting on a system lie in a single
plane. It follows from Newton's Second Law that translational equilibrium occurs
when
 F = 0
If we resolve all the forces acting on a body
into their components along any two perpendicular axes, the equivalent scalar statement
is:
Fx = 0
Fy = 0 |
| A load supported by two ropes.
Since the system is in equilibrium, Fy = 0.
There are two ropes, therefore, sharing the 300 N downward
force.
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| For an object at
static equilibrium, all the forces may act at different locations on the object; however,
the force of gravity always acts at the object's center of mass (cm) or center of gravity
(cg) - these are terms that refer to the point in an object where most of the mass or
weight is concentrated. For example, most of the weight in humans is concentrated in
the abdominal area. In most of the problems we encounter, the center of mass is
given or located at the center of the object. |
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Fy = 0. Hence, no
acceleration. The speed they have reached is called terminal velocity.
