4.2.
Visualize:
Assess:
Note that the climber does not touch the sides of the crevasse so there are no forces from the crevasse walls.
4.4.
Model:
Assume friction is negligible compared to other forces.
Visualize:
4.5.
Visualize:
Please refer to Figure Ex4.5.
Solve:
Mass is defined to be
1
slope of the accelerationversusforce graph
m
=
A larger slope implies a smaller mass. We know
m
2
=
0.20 kg, and we can find the other masses relative to
m
2
by
comparing their slopes. Thus
1
2
12
1/slope 1
slope 2
1
2
0.40
1/slope 2
slope 1
5 2
5
0.40
0.40
0.20 kg
0.08 kg
m
m
mm
==
=
=
=
⇒=
= ×
=
Similarly,
3
2
32
1/slope 3
slope 2
1
5
2.50
1/slope 2
slope 3
2 5
2
2.50
2.50
0.20 kg
0.50 kg
m
m
=
=
=
=
Assess:
From the initial analysis of the slopes we had expected
m
3
>
m
2
and
m
1
<
m
2
. This is consistent with our
numerical answers.
4.6.
Model:
An object’s acceleration is linearly proportional to the net force.
Solve:
(a)
One rubber band produces a force
F
, two rubber bands produce a force 2
F
, and so on. Because
Fa
∝
and two rubber bands (force 2
F
) produce an acceleration of 1.2 m/s
2
, four rubber bands will produce an
acceleration of 2.4 m/s
2
.
(b)
Now, we have two rubber bands (force 2F) pulling two glued objects (mass 2
m
). Using
,
Fm
a
=
2
F
=
(2
m
)
a
a
=
F
/
m
=
0.6 m/s
⇒
2
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 Spring '06
 staff
 Force, Friction, Mass, net force

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