11.2 notes

In other words, all the kinetic energy in a
system plus all the potential energy of a system
is total amount of mechanical energy in the
system.

So, if you calculate that 42% of
the energy a falling object has is
kinetic energy, then ________%
must be potential.
All the kinetic energy plus all the potential energy
before something happens equals all the
kinetic energy plus all the potential energy
after the event.
This is called Conservation of Energy
Kbefore + Ugbefore = Kafter + Ugafter
1/2mv2 + mgh = 1/2mv2 + mgh

Tarzan, mass 85 kg, swings down on the end of
a 20m vine from a tree limb 4.0 m above the
ground.



How fast is Tarzan moving when he reaches the
ground?
Does your answer depend on Tarzan’s mass?
Does your answer depend on the length of the vine?



m = 85 kg
h=4m
l = 20 m
Kinetic energy before is…
Potential energy after is…
Come on, think!
0 + (85)(9.8)(4) = 1/2 (85)v2 + 0
v2 =
v=