Chapter 8 Machines
241
The Wedge
The wedge is a special version of the inclined plane, as shown in
Figure 8-29. It is two inclined planes back-to-back.
The shape is effective because the force exerted pushes out in two
directions as it enters the object. Do you see the difference between
the wedge in Figure 8-29 and the inclined plane in Figure 8-28? Other
applications of the wedge include the plow, a doorstop, the blade of a knife,
and the prow of a boat. See Figure 8-30.
RD x R = ED x E
R
E
Resistance
distance
(RD)
Effort Distance (ED)
gure 8-28. The mass of an object
and the distance it is raised are related
to the length of the inclined plane.
gure 8-30. We use the wedge in many products. A—The wedge-shaped prow (front) of a
ship cuts easily through the water. B—The teeth on the bucket of a backhoe are wedge-shaped
to enter the soil more easily.
A B B B B B B B B B B B B B B
gure 8-29. Because of its shape,
an axe enters material easily and can
split it apart.