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HOMEWORK:
Week 12 – Chapter 13  SOLUTIONS
(13.2)
A person in a rocking chair completes 12 cycles in 21 s. What are the
period and frequency of the rocking?
SOLUTION
12 cycles
0.57 Hz
21 s
11
=
1.8 s
0.571 s
f
T
f
==
(13.11)
An atom in a molecule oscillates about its equilibrium position with a
frequency of
200 10
14
.
×
Hz
and a maximum displacement of 3.50 nm.
(a)
Write an
expression giving
x
as a function of time for this atom, assuming that
x
A
=
at
t
=
0.
(b)
If, instead, we assume that
x
=
0
at
t
=
0,
would our expression for
position versus time use a sine function or a cosine function? Explain.
SOLUTION
(a)
14
14
1
14
1
2.00 10
Hz,
3.50 nm, and
cos
.
24
.
0
0
1
0
s
(3.50 nm)cos[(4.00
10
s
) ]
f
Ax
A
t
f
xt
ω
ωπ
π
−
−
=×
=
=
×
(b)
At
t
= 0,
sin
0
t
=
(13.14)
A mass attached to a spring oscillates with a period of 3.15 s.
(a)
If the
mass starts from rest at
x
=
00440
.
m
and time
t
=
0,
where is it at time
t
=
637
.?
s
(b)
Is the mass moving in the positive or negative
x
direction at
t
=
s
Explain.
SOLUTION
(a)
2
(0.0440 m)cos
.
At
6.37 s,
3.15 s
2 (6.37 s)
(0.0440 m)cos
0.0436 m
3.15 s
t
x
⎛⎞
⎜⎟
⎝⎠
(b)
negative
direction .
x
At
t
= 6.30 s (= 2
T
) the mass was at its largest
displacement in the positive
x
direction. 0.07 s later it is headed toward
the origin.
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View Full Document (13.22)
A peg on a turntable moves with a constant linear speed of 0.67 m/s in a
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This note was uploaded on 07/02/2011 for the course PHYS 201 taught by Professor Woodahl during the Fall '09 term at Indiana.
 Fall '09
 WOODAHL
 Physics, Work

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