Chris jumps off a bridge with a bungee cord (a heavy stretchable cord) tied arou

Question

Chris jumps off a bridge with a bungee cord (a heavy stretchable cord) tied around his ankle, (Figure 1) . He falls for 15 m before the bungee cord begins to stretch. Chris's mass is 72kg and we assume the cord obeys Hooke's law, F=?kx , with 53N/m .

Part A

If we neglect air resistance, estimate what distance d below the bridge Chris's foot will be before coming to a stop. Ignore the mass of the cord (not realistic, however) and treat Chris as a particle. Express your answer to two significant figures and include the appropriate units.

d = ?

Explanation / Answer

delta E = 0

-0.5 k x^2 + m g (h + x) = 0

-0.5(53) x^2 + (72)(9.8) (15 + x) = 0

choose positive value for x,

x = 37.33m

total height

H = h + x

H = 15 + 37.33

H = 52.33 m

distance below the bridge Chris's foot will be before coming to a stop is 52.33 m

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