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Technology: Engineering Our World
Pressure
You have seen how simple machines and gears are able to move a
greater resistance with a smaller effort. Now you will see that pressure
can increase the effort applied. Pressure is the effort applied to a given
area. Figure 8-52A shows a diagram of a simple system for multiplying
force through use of pressure. Figure 8-52B shows a simple pressure
device used to lift an automobile.
To understand how pressure can be increased, think about the area on
which the effort presses. Would you rather a woman step on your foot
with a small, pointed heel or with a larger, flat heel? See Figure 8-53. When
a surface area is small, a little effort produces a large pressure.
gure 8-51. The gears on a
multispeed bicycle allow you to
decrease effort or increase speed.
How is this like the transmission
on an automobile?
Effort Resistance
A B
gure 8-52. Hydraulics use pressure to increase force. A—In a hydraulic system, a fluid transmits effort from where it
is applied to where it is used. B—A hydraulic lift is used to support the mass of an automobile.