# Homework Help: Jumping on a trampoline and energy conserved/ not conserved

1. Oct 16, 2008

### menotyou9

1. The problem statement, all variables and given/known data
So I am jumping on a trampoline and need to look at the different systems and which ones are conserving energy and which ones are not conserving energy. Time-initial= when I am at the lowest point of the trampoline, and Time-final= when I am 1/2 on my way down.
Systems :
me
trampoline
me+earth
me+ trampoline

2. Relevant equations
Work= difference in energy

3. The attempt at a solution
As me as the system I do not conserve energy because I change potential energy.
Trampoline changes potential so it also does not conserve energy
Me and Tramp would be energy conserved because there is no outside force acting on the system.
Me + earth would be energy not conserved because I change energy causing the whole system to change.

So where I've gone wrong and not sure where.

2. Oct 16, 2008

### mgb_phys

The way to look at it is to consider all the ways energy is stored in the system (you+ trampoline).
Kinetic energy - when you are moving
Potential energy - how high you are above the ground
Spring energy - how stretched the trampoline is

At each point in the bounce consider which combination of these has the energy.