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CHAPTER

Statics and Elasticity 14

CONCEPTS IN CONTEXT
Concepts
in
Context Tower cranes are widely used at construction sites. The K-10000 tower
crane shown here is the largest commercially available tower crane. Its 14.1 Statics of Rigid Bodies
central tower is 110 m high, and its long horizontal arm reaches out to 14.2 Examples of Static
84 m. It can lift 120 tons at the end of the long arm, and more than twice Equilibrium
as much at the middle of the long arm.The short arm holds a fixed coun-
14.3 Levers and Pulleys
terweight of 100 tons (at the end, above the arm) and two additional mobile
counterweights (below the arm). For the lift of a small load, the mobile 14.4 Elasticity of Materials
counterweights are parked in the inboard position, near the central tower.
For the lift of a large load, the mobile counterweights are moved outward
to keep the crane in balance.
The concepts discussed in this chapter permit us to examine many
aspects of the operation of such a crane:
? Where must the mobile counterweights be placed to keep the crane
in balance for a given load? (Example 2, page 435)
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