Transcript Bungee Egg Drop Project Week 1

EGR 105
Foundations of Engineering I
Fall 2007 – week 3
Project 1
Bungee Jumping
• Briefly, some theory
• The e-notebook
• In-class experimentation
Initially
• Potential energy
only is present
W = mg
center of gravity
of the jumper
E  mgh
h
During Free Fall
• Fall distance d,
0≤d≤L
d
• Some potential energy
is converted to kinetic,
so
E  mg h  d   2 m v
1
v = velocity
2
During the Stretch
• Now the cord starts to
store energy since d > L
• Energy stored in the
cord equals the integral
of the force f (stretch)
E  m g h  d   12 m v 2

d L
 f ( x)dx
0
original cord length
L (without stretch)
d
stretch = d – L
At the Bottom, distance d0
• Velocity v is now zero, so
mgh  m g h  d 0 

L
d0  L
 f ( x)dx
d0
0
• We could solve for d0 if we
knew f
GOAL!!
v=0
Models for Cords
• Hooke’s Law – linear:
• More realistic model:
f ( x)  kx
– Increasing in x
– f (0) = 0
– Limit for large x
Force f (x)
Stretch x
Assignment #3 – As a Team
• Take measurements of cord characteristic:
– Force scales
– Weights
– Rulers
• Team homework: start your e-notebook
– Sheet 1 – general team info
– Sheet 2 – words and numbers summarizing today’s
measurements
– E-mail the spreadsheet to me
Sample e-notebook