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(c)
The normal force,
n
, is perpendicular to the displacement and thus does zero work.
Reflect:
Friction does positive work and gravity does negative work. The net work done is zero.
7.12. Set Up:
Use
to calculate
where
K
is equal to the change in thermal energy.
Solve: (a)
(b)
Reflect:
When the mass increases by a factor of two, the speed required decreases by a factor of
7.13. Set Up:
Use
and solve for
m
.
Solve:
Reflect:
The kinetic energy of an object is proportional to the mass of the object.
7.14. Set Up:
Use
to relate and
K
.
Solve: (a)
(b)
K
is proportional to
so
K
increases by a factor of 4 when
doubles.
7.15. Set Up:
Use
to relate and
K
. Let
and
be speed and kinetic energy when
Solve: (a)
and
so
(b)
Since
we obtain
This means that the decrease in
K
is
7.16. Set Up:
Applying
to relate and
K
results in
Solve: (a)
where
and
Substituting,
(b)
Now let
and
Substituting,
Reflect:
When
K
changes by a factor of two, the speed
changes by a factor of
When
changes by a factor of
two, the kinetic energy changes by a factor of
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This note was uploaded on 03/06/2009 for the course PHYS 114 taught by Professor Shoberg during the Spring '07 term at Pittsburg State Uiversity.
 Spring '07
 Shoberg
 Force, Friction, Gravity, Work

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