32 - Work

# 32 - Work - Work If an object is moved a distance d using a...

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Work If an object is moved a distance d using a constant force, W = F ! d (Force)(distance). The units are either foot-pounds (ft-lb) or Newton meters = joules. Work is only done when moving the object. Ex. How much work is done by a weightlifter in raising a 60 kg barbell from the floor a height of 2 meters?

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Suppose we use a variable force, F(x), which depends on position. W i = F x i ( ) ! x Total work = W = Springs: Hooke’s Law: F(x) = kx The force necessary to keep a spring stretched or compressed x units beyond (or short of) its natural length is proportional to x.
Ex. A force of 8 lb. Is required to keep a spring compressed 1/2 ft. below its normal length. Find k and the work done. Ex. A spring has a natural length of .5 m. A force of 50N stretches the spring to a length of .6 m. a. What force is needed to stretch the spring x m ? b. How long is the spring when stretched by a force of 200 N? c. Find the work done in stretching the spring .2 m.

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32 - Work - Work If an object is moved a distance d using a...

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