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1
Chap 7
Work and kinetic energy
Note – this is an outline of the lecture, print this
and take notes on it in lecture It is not the
and take notes on it in lecture. It is not the
complete lecture.
You should attend lecture to
get the complete notes
Images taken from Halliday/Resnick/Walker,
Fundamentals of Physics, 7
th
Edition, John Wiley
and Sons Inc., by permission.
Hints:
Checkpoint 1
:
Δ
K =W
.
Note that
K
can never be
negative,
Δ
K
can be positive or negative.
P.9
. You can start out with
and then find the initial (
v
0
) and
final (
v
) velocities.
To find the
v
, first find the
acceleration from the information given, then find
v
.
P19.
The tension
T
(cord force) is not equal to
mg
since the
block has an acceleration.
You must find the tension
using Newton’s second law before you can find the work
done by the tension.
P50 b)
Note:
k
= 2.5 N/cm = 250 N/m,
d)
.
You will have to
solve a quadratic equation
P71.
The zero on the scale is not the equilibrium position of
the untensioned spring.
Call the untensioned position
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 Spring '08
 oshea
 Energy, Kinetic Energy, Work

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