Report

Monday,
March 23, 2009

9:41 PM

The rubber band
chain is made of rubber bands looped together and the mass is a .15kg mass
hanger. The drop was 4.8 m high allowing for the height of the mass hanger.

In order to predict the
number of rubber bands we first had to answer:

What is the spring constant of the bungee cord as a function
of the number of rubber bands?

To find this we had
use the understand what the energy levels were at key points in the
problem.

The first key point is the top of the situation, before
release.  Here all of the energy is
potential (mgh)

The second key point is
where the object has fallen the length of the rubber bands.  At this point in time there is no
effect from the spring.  This is
where the object would stop if we used a string.

The third key point is where
the spring is fully extended.  This
point should be right above the floor.  At this point there is no gravitational
potential energy or kinetic energy since the object is not moving.  There is only spring potential energy.

We know that this is
equal to the gravitational potential energy at point 1 because of conservation
of energy.

To fill in the
variables we need to know:

The spring constant; will
find below

In order to find the
spring constant, we need to test the stretched and unstretched length of rubber
band chains of different lengths.  We
created a rubber band chain by looping the rubber bands inside of each other.  We then held a rubber band chain up against a
meter stick so that it would hang freely.
This was the unstretched length.
We then attached the .15kg mass hanger and recorded the
"stretched" length.

We then used a TI-89
to solve for n.  This actually took the
calculator a minute to process.

It returned that we
needed 28 rubber bands