Transcript Ch 12 Worksheet

Chapter 12
Review
Waves
1. What is
simple
harmonic
motion?
Motion when an
object is disturbed
and the restoring
force follows the
formula F = -kx.
2. Which of these are examples of
simple harmonic motion?
A. a pendulum
B. a weight on a spring
C. a “plucked” guitar string
D. a weightlifter doing five
repetitions
E. an oboe player tapping her foot
F. a bouncing ball
2. Which of these are examples of
simple harmonic motion?
A. a pendulum
B. a weight on a spring
C. a “plucked” guitar string
D. a weightlifter doing five
repetitions
E. an oboe player tapping her foot
F. a bouncing ball
3a. A mass on a spring
is oscillating. Describe
the net force,
acceleration, and
velocity of the mass
when it crosses the
equilibrium position.
The net force is
and acceleration
are zero. The
velocity is at its
maximum.
3b. Describe the net
force, acceleration,
and velocity of the
mass when it is at the
point of maximum
displacement.
The net force and
the acceleration
are at their
maximum. The
velocity is at zero.
4. What is the spring
constant of a spring if
a force of 100 N
stretches the spring
20 cm?
F = kx
100 N = k(.2 m)
k= 500 N/m
5. A spring is
compressed 10 cm. If
the restoring force is
200 N, what is the
spring constant?
F = kx
200 = k(0.1 m)
2000 N/m = k
6. A weight oscillating on a
spring is held next to a
meter stick. If the center of
mass of the weight
oscillates from the 10 cm
point to the 40 cm point,
what is the amplitude of
the oscillation?
The distance of oscillation from
maximum displacement to
maximum displacement is
30 cm. The equilibrium position
is halfway between. Since
amplitude is from equilibrium
position to maximum
displacement, the amplitude is
15 cm.
7. A pendulum
swings through a
total angle of 38°.
What is the angle
of amplitude?
Half the total,
19°.
8. How does
period relate
to frequency?
T = 1/f or
f = 1/T
9. How does
period relate
to amplitude?
Period and
amplitude are
NOT related to
each other.
10. If the
frequency of an
oscillator is
20 Hz, what is
the period?
T = 1/f
T = 1/20
T = 0.05 s
11. How should you
change the length
of a pendulum to
double the period?
T = 2π√(l/g)
If I want the period T to
double, the √(l/g) must be 2
times as much, therefore the
length l must be increased to
four times the length,
because the √4 is 2.
12. What is the period
of a 2 kg mass in
simple harmonic motion
with an amplitude of
20 cm if the spring
constant is 400 N/m?
What is the frequency?
T = 2π√(m/k)
T = 2π√(2/400)
T = 0.44 s
f = 1/T = 1/0.44
f = 2.25 Hz
13. How would the
period in problem
12 change if the
amplitude were 40
cm?
None, amplitude
doesn’t affect
period or
frequency.
14. What is
the period
of a 2 m
pendulum?
T = 2π√(l/g)
T = 2π√(2/10)
T = 2.8 s
15. What would be
the period of the
same 2 m
pendulum on the
moon where g is
1/6th as much?
T = 2π√(l/g)
T = 2π√[2/(10/6)]
T = 6.9 s
16. Describe the
motion of a single
particle in a
transverse wave.
In a transverse
wave the particles
move perpendicular
to the direction of
the wave.
17. Describe the
motion of a single
particle in a
longitudinal wave.
In a longitudinal
wave the particles
move parallel to the
direction of the
wave.
18. Which type
of wave are
sound waves?
Sound waves
are
longitudinal.
19. What is the
speed of a sound
wave if the
frequency is 512 Hz
and the wavelength
is 0.7 m?
v=fl
v = 512 x 0.7
v = 358 m/s
20. If a wave travels 14
m/s and a floating duck
bobs up and down once
every 3 seconds, what
is the wavelength of the
wave?
3 seconds is the period, T = 1/f,
so the frequency is 1/3 Hz
v=fl
14 = 1/3 x l
l = 42 m
21. What is the
difference in
constructive and
destructive
interference?
In constructive
interference the
amplitude is increased;
in destructive
interference the
amplitude is decreased.
22. Which of these are examples of
constructive interference and which of
these are examples of destructive
interference?
A. noise-canceling headphones
B. a “dead spot” in a movie theater
C. an earthquake causes a building
to fall
D. a singer breaks a glass with his
voice
22. Which of these are examples of
constructive interference and which of
these are examples of destructive
interference?
D
D
C
C
A. noise-canceling headphones
B. a “dead spot” in a movie theater
C. an earthquake causes a building
to fall
D. a singer breaks a glass with his
voice
23. What are
fixed-end
termination and
free-end
termination?
Fixed-end there is a
change in phase at
reflection.
Free-end there is
no change in phase
at reflection.
24. What is a
standing
wave?
When two waves of
the same amplitude
and frequency cross
over each other and
produce pattern of
loops and nodes.
25. Draw a string
vibrating at the 3rd
harmonic. How many
nodes are present?
How many antinodes
are present? How many
loops are present?
Three loops and
antinodes (same
thing), four nodes.
26. Draw a
transverse wave.
Label the crest,
trough, wavelength,
and amplitude.
Crests are the high
points, troughs are
the low points.