What is the spring constant?

A 2.0 g spider is dangling at the end of a silk thread. You can make the spider bounce up and down on the thread by tapping lightly on his feet with a pencil. You soon discover that you can give the spider the largest amplitude on his little bungee cord if you tap exactly once every second.

Amplitude is maximum when the freq. of applied force is equal to the natural frequency of oscillation(also called Resonance).
Hence pd pf osc = 1sec.

=> 2*pi*sqrt(m/k)=1
=> 4*pi^2*m/k=1
or k=4*pi^2*m
=4*9.9*.002
=0.079N/m

Spider Bungee Cord

T = 2 pi sqrt(m/k)
You know the mass (0.0020kg), the period (1s), solve for k.

Source(s): My website, studyphysics.ca , on the Physics 20 Note-A-Rific page, lesson 44.