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47. (a) We take the initial gravitational potential energy to be
U
i
= 0. Then the final
gravitational potential energy is
U
f
= –
mgL
, where
L
is the length of the tree. The change
is
UU
m
g
L
fi
−=
−
=
−
=
−×
((
.
25
12
2 9 10
3
kg) 9.8 m s
m)
J .
2
di
(b) The kinetic energy is
22
2
11
(25 kg)(5.6 m/s)
3.9 10 J
Km
v
==
=
×
.
(c) The changes in the mechanical and thermal energies must sum to zero. The change in
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This note was uploaded on 05/17/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.
 Spring '08
 Any
 Physics, Energy, Potential Energy

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