Problem 1.
(32 points)
Answer the following questions and
give brief explanations for your answers
. Just stating
the answer without explanation is not sufficient. Note, there are also questions on the back of
this page. Answer all the parts! Each question is worth 4 points unless stated otherwise.
(a)
Two identical disks,
A
and
B
, roll across a floor with equal speeds. Disk
A
then rolls up an
incline without slipping, reaching a height
h
. Disk
B
moves up an incline that is identical
except for the fact that it is frictionless. Is the maximum height that disk
B
reaches greater
than, less than, or equal to
h
?
A
B
CM
(b)
A uniform block is suspended by two wires,
A
and
B
, which are identical
except for their initial lengths. The center of mass of the block is closer to
wire
B
than wire
A
as shown in the figure at the right.
(1)
Which wire exerts
a larger force on the block?
(2)
If the two wires end up the same length,
which one started out shorter?
(c)
A 100 kg mass is suspended by a steel wire with diameter 6
.
0 mm and length 10 m. You
measure that the wire stretches 1
.
6 mm under this load. What is Young’s modulus for the
steel used in this wire?
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 Spring '08
 kernan
 mechanics, Mass, General Relativity

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