Energy and Momentum Methods for Rigid Bodies in Plane Motion

Newtons second law in determining kinetics relationships is not always
the most ef?cient, although it always works. As for particles, energy
and momentum methods are often useful to analyze
rigid bodies in plane motion.

Work of a Force on a Rigid Body

The work of a δύναμη acting on a rigid body moving from position 1 to 2 is

Work of a Moment

Το work of a moment has a similar form, for Γωνιακή positions ?,

In the common case where the moment vector M is perpendicular
to the plane of motion,
M ? d? = M d?.
It is important to note those δυνάμεις that do no work:
1. δυνάμεις that act at ?xed points on the body do not do work.
For example, the reaction at a ?xed, frictionless pin does no work
on the body that rotates about that pin.
2. Ένα δύναμη which is always perpendicular to the direction of the
motion does no work.
3. The weight of a body does no work when the bodys center
of gravity moves in a horizontal plane.
4. The friction δύναμη ^ at a point of contact on a body that rolls
without slipping does no work. This is because the point of contact
is the instantaneous center of zero velocity.
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Prefabricated ceiling tiles are attached either to an existing ceiling or to furring strips. Staples or nails, either with or without adhesive, or adhesive alone secures the tiles.

Often, ceiling tiles show the effect of water damage. To conceal stains or streaks in tiles, apply a primer or clear sealer. When the tiles are dry, you can paint them with latex paint.

Another problem you may en-counter is dents or chips in tiles. Illus-trated at right are the steps in removing and replacing a dented tile with tongue-and-groove edges. You cut through all four joints and pry the tile off its backing; pry out the cut-off tongues from the grooves in the adjacent tiles. Use pliers to remove remaining staples or nails; scrape off adhesive.
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Repairing Wood Floors
Replacing Wood Flooring
Silencing Squeaky Floors

A good wood floor will last the life of your home and actually improve with age. But even the best wood floors are subject to damage or other problems.

The problem may be in the surface flooring or related to defects in the supporting structure. To successfully repair the floor, it’s important to know what type of flooring you have and how it’s attached to the subfloor, as well as the cause of the damage or problem.

Flooring structure, types of wood flooring, and common problems are described below. On the following
pages you’ll find directions for repairing surface damage, fixing individual boards, replacing damaged sections of flooring, and silencing squeaky floors both from the surface and from underneath.

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