
Concept explainers
A bungee cord is essentially a very long rubber band that can stretch up to four times its unstretched length. However, its spring constant vanes over its stretch [see Menz, P.G. “The Physics of Bungee Jumping.” The Physics Teacher (November 1993) 31: 483-487]. Take the length of the cord to be along the direction and define the stretch
as the length of the cord
minus its un-stretched length
that is,
(see below). Suppose a particular bungee cord has a spring constant, for
of
and for. (Recall that the
of
(Recall that the spring constant is the slope of the force
versus its stretch
(a) What is the tension in the cord when the stretch is 16.7 m (the maximum desired for a given jump)? (b) How much work must be done against the elastic force of the bungee cord to stretch It 16.7 m?
Figure 7.16 (credit modification of work by Graeme Churchard)

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