Physics Homework Question?

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 78 kg and we assume the cord obeys Hooke's law, F=−kx, with 56 N/m .

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.

Answer 1

Step 1:

The mass of the Chris is .

Chris falls for before the bungee cord begins to stretch.

The cord obeys Hookes law, .

Hookes constant is .

Draw the figure for the situation:

.

Step 2:

The potential energy of the person is .

The potential energy of the person after the bungee cord begins to stretch is .

Total potential energy below the bridge is .

.

The distance below the bridge and Chris foot before coming to a stop is .

The distance below the bridge and Chris foot before coming to a stop is .

Solution:

The distance below the bridge and Chris foot before coming to a stop is .