Serway_CP_poll_chapter_13_ Physics_ mechanics.ppt

answer for a physics book chapter

1. A 2.0 kg block is attached to a spring that obeys Hooke's
Law. An amount of energy, 16 J, is done to stretch the spring.
The block is then released and oscillates with a period of 0.30
s. What is the amplitude of the motion?
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1.38.0 cm
2.19.0 cm
3.9.5 cm
4.4.3 cm

2. A 0.20 kg block rests on a frictionless level surface and is
attached to a horizontally aligned spring with a spring
constant of 40 N/m. The block is initially displaced 4 cm from
the equilibrium point and then released to set up a simple
harmonic motion. What is the speed of the block when it
passes through the equilibrium point?
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1.2.13 m/s
2.1.62 m/s
3.1.10 m/s
4.0.57 m/s

3. A runaway railroad car, with mass 30 x 10
4
kg, coasts across
a level track at 2.0 m/s when it collides with a spring loaded
bumper at the end of the track. If the spring constant of the
bumper is 2 x 10
6
N/m, what is the maximum compression of
the spring during the collision? (Assume collision is elastic.)
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1.0.77 m
2.0.58 m
3.0.34 m
4.1.07 m

4. A mass of 0.4 kg, hanging from a spring with a spring
constant of 720 N/m, is set into an up-and-down simple
harmonic motion. What is the potential energy stored in
the spring alone when the mass is displaced 0.1 m?
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1.zero
2.1.8 J
3.3.6 J
4.7.2 J

5. A mass of 0.4 kg, hanging from a spring with a spring
constant of 80 N/m, is set into an up-and-down simple
harmonic motion. What is the speed of the 0.2 kg mass when
moving through the equilibrium point? The starting
displacement is 0.1 m.
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1.zero
2.1.4 m/s
3.2.0 m/s
4.3.4 m/s

6. A mass of 0.4 kg, hanging from a spring with a spring
constant of 80 N/m, is set into an up-and-down simple
harmonic motion. What is the speed of the 0.2 kg mass
when moving through a point at 0.05 m displacement? The
starting displacement is 0.1 m.
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1.zero
2.1.4 m/s
3.1.7 m/s
4.1.2 m/s

7. A mass of 0.4 kg, hanging from a spring with a spring
constant of 80 N/m, is set into an up-and-down simple
harmonic motion. What is the acceleration of the mass
when at its maximum displacement of 0.1 m?
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1.zero
2.5 m/s
2
3.10 m/s
2
4.20 m/s
2

8. . A car with bad shocks bounces up and down with a
period of 1.5 seconds after hitting a bump. The car has
a mass of 1500 kg and is supported by four springs of
force constant k. What is k for each spring?
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1.6580 N/m
2.5850 N/m
3.4440 N/m
4.3630 N/m

9. A simple pendulum has a mass of 0.25 kg and a length
of 1 m. It is displaced through an angle of 30° and then
released. After a time, the maximum angle of swing is
only 10°. How much energy has been lost to friction?
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1.0.29 J
2.0.65 J
3.0.8 J
4.1.0 J

10. A 2-m long piano string of mass 10 grams is
under a tension of 338 N. Find the velocity with
which a wave travels on this string.
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1.130 m/s
2.260 m/s
3.520 m/s
4.1040 m/s

11. Transverse waves travel with a speed of 200 m/s along
a taut copper wire that has a diameter of 1.5 mm. What
is the tension in the wire? (The density of copper is 8.93
grams/cm
3
.)
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1.1893 N
2.1262 N
3.631 N
4.315 N

12. An earthquake emits both P-waves and S-waves which
travel at different speeds through the Earth. A P-wave travels
at 9000 m/s and an S-wave at 5000 m/s. If P-waves are
received at a seismic station 1 minute before an S-wave
arrives, how far to the earthquake center?
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1.2420 km
2.1210 km
3.680 km
4.240 km

13. The motion of a piston in an automobile engine is nearly
simply harmonic. If the 1 kg piston travels back and
forth over a total distance of 10 cm, what is its
maximum velocity when the engine is running at 3000
rpm?
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1.31.4 m/s
2.15.7 m/s
3.7.8 m/s
4.3.9 m/s

14. Waves propagate along a stretched string with a speed
of 8 m/s. The end of the string is vibrated up and down
once every 1.5 s. What is the wavelength of the waves
that travel along the string?
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1.3.0 m
2.12.0 m
3.6.0 m
4.5.33 m

15. Consider two identical wave pulses on a string. Suppose the first
pulse reaches the fixed end of the string and is reflected back and
then meets the second pulse. When the two pulses overlap exactly,
the superposition principle predicts that the amplitude of the
resultant pulses, at that moment, will be what factor times the
amplitude of one of the original pulses?
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1.0
2.1
3.2
4.4

16. An ore car of mass 4000 kg rolls downhill on tracks from a
mine. At the end of the tracks, at 10 m elevation lower is a
spring with k = 400,000 N/m. How much is the spring
compressed in stopping the ore car? Ignore friction.
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1.0.14 m
2.0.56 m
3.1.40 m
4.1.96 m

17. Bats can detect small objects such as insects that are of a
size approximately that of one wavelength. If bats emit a
chirp at a frequency of 60 kHz, and the speed of
soundwaves in air is 330 m/s, what is the smallest size
insect they can detect?
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1.1.5 mm
2.3.5 mm
3.5.5 mm
4.7.5 mm

18. Consider the curve f = 3 cos(2px/I). The
wavelength of the wave will be
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1.the distance O to A.
2.twice the distance O to A.
3.the distance x
2 to x
3.
4.twice the distance x
2 to x
3.

19. Tripling the mass of the bob on a simple
pendulum will cause a change in the frequency
of the pendulum swing by what factor?
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1.0.33
2.1.0
3.3.0
4.9.0

20. By what factor must one change the weight
suspended vertically from a spring coil in order
to triple its period of simple harmonic motion?
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1.1/9
2.0.33
3.3.0
4.9.0

21. Tripling the displacement from equilibrium of an object
in simple harmonic motion will bring about a change in
the magnitude of the object's acceleration by what
factor?
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1.0.33
2.1.0
3.3.0
4.9.0

22. By what factor should the length of a
simple pendulum be changed if the period
of vibration were to be tripled?
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1.1/9
2.0.33
3.3.0
4.9.0

23. Which one of the following quantities is at a
maximum when an object in simple harmonic
motion is at its maximum displacement?
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1.velocity
2.acceleration
3.kinetic energy
4.frequency

24. The wavelength of a traveling wave is a
function of which of the following?
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1.frequency
2.velocity
3.both frequency and
velocity are valid
4.amplitude

25. A coil spring, with a spring constant of
120 N/m, will be stretched to what
displacement by a 60 N force?
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1.0.5 m
2.2.0 m
3.4.0 m
4.7200 m

26. If one could transport a simple pendulum of constant
length from the Earth's surface to the moon's, where the
acceleration due to gravity is one-sixth (1/6th) that on the
Earth, by what factor would the pendulum frequency be
changed?
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1.almost 6.0
2.almost 2.5
3.almost 0.4
4.almost 0.17

27. The tension in a guitar string is increased
by a factor of two. By what factor does the
wave velocity change?
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1.2.0
2.1.4
3.0.7
4.0.5

28. If the frequency of a traveling wave train is increased by
a factor of three in a medium where the velocity is
constant, which of the following is the result?
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1.amplitude is one-third
as big
2.amplitude is tripled
3.wavelength is one-
third as big
4.wavelength is tripled

29. What is the phase difference when two
waves, traveling in the same medium,
undergo constructive interference?
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1.270°
2.180°
3.90°
4.0°

30. The kinetic energy of the bob on a simple pendulum
swinging in simple harmonic motion has its maximum
value when the displacement is at what point in its
swing?
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1.zero displacement
2.1/4 the amplitude
3.1/2 the amplitude
4.equals the
amplitude

31. Tripling the weight suspended vertically from a coil
spring will result in a change in the displacement of the
spring's lower end by what factor?
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1.0.33
2.1.0
3.3.0
4.9.0

32. A 0.2 kg object is suspended from a spring with spring
constant, k = 10 N/m, and moves with simple harmonic
motion. At the instant that it is displaced from
equilibrium by -0.05 m, what is its acceleration?
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1.1000 m/s
2
2.40 m/s
2
3.0.1 m/s
2
4.2.5 m/s
2

33. A 0.2 kg object is suspended from a spring with a spring
constant of k = 10 N/m. The object moves with simple
harmonic motion and has an amplitude of 0.08 m. What is
the potential energy of the system when the object
displacement is 0.08 m?
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1.0.40 J
2.zero
3.3.2 x 10
-2
J
4.62.5 J

34. A 0.2 kg object, suspended from a spring with a spring
constant of k = 10 N/m, is moving in simple harmonic
motion and has an amplitude of 0.08 m. What is its velocity
at the instant when its displacement is 0.04 m? (Hint: Use
conservation of energy.)
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1.9.8 m/s
2.4.9 m/s
3.49.0 cm/s
4.24.5 cm/s

35. If a force of 50 N stretches a spring 0.10
m, what is the spring constant of the
spring?
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1.5.0 N/m
2.500 N/m
3.0.002 N/m
4.0.25 N/m

36. Replacing an object on a spring with one of nine times
the mass will have the result of changing the frequency
of the vibrating spring by what factor?
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1.1/9
2.0.33
3.3.0
4.9.0

37. A simple pendulum of length 1 m has a mass of 100
grams attached, is drawn back 30° and then released.
What is the maximum velocity of the mass?
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1.1.14 m/s
2.3.13 m/s
3.2.21 m/s
4.1.62 m/s

38. Consider the curve x = A sin(kt), with A >
0. At which point on the graph below is it
possible that t = 0?
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1.Point A
2.Point B
3.Point C
4.Point D

39. Suppose a 0.30 kg mass on a spring-loaded gun that has
been compressed 0.10 m has elastic potential energy of
1.0 J. How high above the spring's equilibrium point can
the gun fire the mass if the gun is fired straight up?
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1.0.10 m
2.3.3 m
3.0.34 m
4.10 m

40. As a gust of wind blows across a field of grain, a wave
can be seen to move across the field as the tops of the
plants sway back and forth. This wave is a
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1.transverse wave
2.longitudinal wave
3.polarized wave
4.interference of
waves

41. For a wave on the ocean, the
amplitude is
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1.the distance between crests.
2.the height difference between
a crest and a trough.
3.one-half the height difference
between a crest and a trough.
4.how far the wave goes up on
the beach.

42. For a mass suspended on a spring in the
vertical direction, the time for one
complete oscillation will depend on
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1.the value for g (the
acceleration of gravity).
2.the distance the mass
was originally pulled
down.
3.the maximum speed of
the oscillating mass.
4.none of these.

43. Suppose a 0.3 kg mass on a spring that has
been compressed 0.10 m has elastic potential
energy of 1 J. What is the spring constant?
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1.10 N/m
2.20 N/m
3.200 N/m
4.300 N/m

44. Suppose a 0.3 kg mass on a spring that has been
compressed 0.10 m has elastic potential energy of 1.0
J. How much further must the spring be compressed to
triple the elastic potential energy?
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1.0.30 m
2.0.20 m
3.0.17 m
4.0.07 m

45. Which is not an example of approximate
simple harmonic motion?
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1.A ball bouncing on the
floor.
2.A child swinging on a
swing.
3.A piano string that has
been struck.
4.A car's radio antenna as it
waves back and forth.

46. Tripling the tension in a guitar string will
result in changing the wave velocity in the
string by what factor?
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1.0.58
2.1.00
3.1.73
4.3.00

47. Tripling the density, in mass per unit length, of a
guitar string will result in changing the wave
velocity in the string by what factor?
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1.0.58
2.1.00
3.1.73
4.3.00

48. If a wave pulse is reflected from a free
boundary, which of the following choices best
describes what happens to the reflected pulse?
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1.becomes inverted
2.remains upright
3.halved in amplitude
4.doubled in
amplitude

49. A radio wave has a speed of 3 x 10
8
m/s
and a frequency of 107.7 MHz. What is its
wavelength?
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1.3.21 m
2.45.0 m
3.0.10 m
4.2.78 m

50. An object moving in simple harmonic motion has an
amplitude of 0.02 m and a maximum acceleration of 40
m/s
2
. What is the frequency of the system?
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1.0.60 Hz
2.51.0 Hz
3.7.1 Hz
4.16.0 Hz

51. Suppose there is an object for which F = +kx.
What will happen if the object is moved away
from equilibrium (x = 0) and released?
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1.It will return to the
equilibrium position.
2.It will move further away
with constant velocity.
3.It will move further away
with constant acceleration.
4.It will move further away
with increasing acceleration.

52. A mass on a spring vibrates in simple harmonic motion at
a frequency of 4.0 Hz and an amplitude of 8.0 cm. If a
timer is started when its displacement is a maximum
(hence x = 4 cm when t = 0), what is the displacement of
the mass when t = 3.7 s?
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1.zero
2.0.025 m
3.0.036 m
4.0.080 m

53. A mass on a spring vibrates in simple harmonic motion
at a frequency of 4.0 Hz and an amplitude of 8.0 cm. If
the mass of the object is 0.20 kg, what is the spring
constant?
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1.40 N/m
2.87 N/m
3.126 N/m
4.160 N/m

54. A mass on a spring vibrates in simple harmonic motion at
a frequency of 4.0 Hz and an amplitude of 8.0 cm. If a
timer is started when its displacement is a maximum
(hence x = 4 cm when t = 0), what is the acceleration
magnitude when t = 3 s?
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1.zero
2.0.13 m/s
2
3.0.33 m/s
2
4.0.51 m/s
2

55. If a simple pendulum has a period of 2.0
s, what is the pendulum length? (g = 9.8
m/s
2
)
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1.0.36 m
2.0.78 m
3.0.99 m
4.2.45 m

56. A traveling wave train has a wavelength
of 0.50 m and a speed of 20 m/s. What is
the wave frequency?
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1.0.025 Hz
2.20 Hz
3.40 Hz
4.10 Hz

57. A musical tone, sounded on a piano, has
a frequency of 410 Hz and a wavelength
in air of 0.80 m. What is the wavespeed?
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1.170 m/s
2.235 m/s
3.328 m/s
4.587 m/s

58. The oxygen molecule (O
2
) may be regarded as two masses
connected by a spring. In vibrational motion, each oxygen atom
alternately approaches, then moves away from the center of mass
of the system. If each oxygen atom of mass (m = 2.67 x 10
-26
kg)
has a vibrational energy of 1.6 x 10
-21
J, and the effective spring
constant is 50 N/m, then what is the amplitude of oscillation of each
oxygen atom?
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1.3.2 x 10
-11
m
2.1.6 x 10
-11
m
3.1.1 x 10
-11
m
4.8.0 x 10
-12
m

59. A mass on a spring vibrates in simple harmonic motion at a
frequency of 4.0 Hz and an amplitude of 8.0 cm. If a timer is
started when its displacement is a maximum (hence x = 4 cm
when t = 0), what is the speed of the mass when t = 3 s?
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1.zero
2.0.0065 m/s
3.0.015 m/s
4.0.024 m/s

60. A 0.20 kg block rests on a frictionless level surface and is
attached to a horizontally aligned spring with a spring constant of
40 N/m. The block is initially displaced 4 cm from the equilibrium point
and then released to set up a simple harmonic motion. Suppose that
a frictional force of 0.3 N exists between the block and surface. What
is the speed of the block when it passes through the equilibrium point
after being released from the 4.0 cm displacement point?
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1.0.45 m/s
2.0.63 m/s
3.0.80 m/s
4.1.16 m/s