fryer (vdf96) – Assignment 5.5 Uniform Circular Motion – graves – (6)
1
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printout
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have
16
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001(part1of2)10.0points
An amusement park ride consists of a rotating
circular platform 11 m in diameter from which
10 kg seats are suspended at the end of 2
.
87 m
massless chains.
When the system rotates,
the chains make an angle of 33
.
7
◦
with the
vertical.
The acceleration of gravity is 9
.
8 m
/
s
2
.
θ
l
d
What is the speed of each seat?
Correct answer: 6
.
80841 m
/
s.
Explanation:
In the vertical direction we have
T
cos
θ
=
m g ,
where
T
is the tension in the chain.
In the
horizontal direction we have
T
sin
θ
=
m v
2
r
.
Since
r
=
ℓ
sin
θ
+
d
2
= (2
.
87 m) sin 33
.
7
◦
+
11 m
2
= 7
.
0924 m
,
we have
v
=
radicalbig
g r
tan
θ
=
radicalBig
(9
.
8 m
/
s
2
) (7
.
0924 m) tan 33
.
7
◦
= 6
.
80841 m
/
s
.
002(part2of2)10.0points
If a child of mass 33
.
6 kg sits in a seat, what is
the tension in the chain (for the same angle)?
Correct answer: 513
.
586 N.
Explanation:
M
= 33
.
6 kg
From the first part we have
T
cos
θ
= (
m
+
M
)
g
T
=
(
m
+
M
)
g
cos
θ
=
(10 kg + 33
.
6 kg) (9
.
8 m
/
s
2
)
cos 33
.
7
◦
= 513
.
586 N
.
003
10.0points
As viewed by a bystander, a rider in a “barrel
of fun” at a carnival finds herself stuck with
her back to the wall.
ω
Which diagram correctly shows the forces
acting on her?
1.
2.
None of the other choices
3.
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fryer (vdf96) – Assignment 5.5 Uniform Circular Motion – graves – (6)
2
4.
5.
6.
correct
Explanation:
The normal force of the wall on the rider
provides the centripetal acceleration neces
sary to keep her going around in a circle. The
downward force of gravity is equal and oppo
site to the upward frictional force on her.
Note:
Since this problem states that it is
viewed by a bystander, we assume that the
freebody diagrams are in an inertial frame.
004
10.0points
A ball rolls around a circular wall, as shown
in the figure below. The wall ends at point
X
.
A
B
C
D
E
X
When the ball gets to
X
, which path does
the ball follow?
1.
Path
B
2.
Path
C
correct
3.
Path
D
4.
Path
A
5.
Path
E
Explanation:
As soon as the ball reaches point X the
centripetal force is removed, so the ball moves
in a straight line (tangent to the circle at oint
X).
Path
C
is the correct answer.
005
10.0points
When you are in the front passenger seat of a
car turning to the left, you may find yourself
pressed against the rightside door.
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 Fall '10
 Graves
 Physics, Centrifugal Force, Circular Motion, Force, Sin, Correct Answer, fryer

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