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Version One – Homework 9 – savrasov – 39822 – Nov 13, 2007
1
This printout should have 8 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
The due time is Central
time.
Sphere Held Against a Wall 01
12:01, trigonometry, numeric,
>
1 min, fxed.
001
(part 1 oF 3) 1 points
A solid sphere oF radius
R
and mass
M
is
held against a wall by a string being pulled at
an angle
θ . f
is the magnitude oF the Frictional
Force and
W
=
M g .
W
P
F
θ
R
Towhatdoesthetorqueequation
X
i
~
τ
i
= 0
about point
O
(the center oF the sphere) lead?
1.
F
=
f
correct
2.
F
+
W
=
f
3.
F
cos
2
θ
=
f
4.
F
sin
θ
=
f
5.
F
sin
θ
cos
θ
=
f
6.
W
=
f
Explanation:
W
P
F
θ
R
R
f
Applying rotational equilibrium about
O
,
the center oF the sphere,
X
i
~
τ
i
= 0i, so
τ
c
=
τ
cc
F R
=
f R
F
=
f .
002
(part 2 oF 3) 1 points
To what does the vertical component oF the
Force equation lead?
1.
F
sin
θ
+
f
=
W
correct
2.
F
sin
θ
=
W
3.
F
cos
θ
+
W
=
f
4.
F
sin
θ
=
f
5.
F
sin
θ
=
f
+
W
Explanation:
Applying translational equilibrium verti
cally,
X
i
F
yi
=
F
sin
θ
+
f
W
= 0
F
sin
θ
+
f
=
W
.
003
(part 3 oF 3) 1 points
±ind the smallest coe²cient oF Friction
μ
needed For the wall to keep the sphere From
slipping.
1.
μ
=
1
cos
θ
correct
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View Full DocumentVersion One – Homework 9 – savrasov – 39822 – Nov 13, 2007
2
2.
μ
= sin
θ
3.
μ
= cos
θ
4.
μ
= tan
θ
5.
μ
=
1
sin
θ
6.
μ
=
1
tan
θ
Explanation:
Let
N
be the normal force.
f
≤
μ N
; when
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 Fall '09
 RichardScalettar
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