Excursions in Physics
PHY 3050C
Third Hour Exam

November 4, 1999

Low: 44

Enter all your answers in the "scantron sheet" or the "bubble sheet". Turn in only that sheet. Anything you write on this exam will not be seen or used or considered or graded. Be sure your name is on the "bubble sheet" you hand in. Be sure your name is bubbled-in. Be sure your answers are recorded correctly.
For every question, also consider the following as a possible answer:
e) none of the above

Possibly useful information:

 v = x / t a = v / t v = vi + a t x = xi + vi t + (1/2) a t2 v = r F = m a F12 = &endash; F21 w = mg g = 9.8 m/s2 10 m/s2 p = m v PEg = m g h PEspg = (1/2) k x2 KE = (1/2) m v2 F = k x Etot = KE + PE Ei = Ef pi = pf Fc = m v2 / r F = p / t T = 2 · T = 2 · v = v = (wavelength) x (frequency) L = (n) x (half wavelength)

For every question, also consider the following as a possible answer:
e) none of the above

1. Increasing the amplitude of a mass-and-spring simple harmonic oscillator makes its period

A) longer

B) shorter

C) unchanged

2. Increasing the spring constant k (that is, using a stronger spring) in a mass-and-spring simple harmonic oscillator makes its period

A) longer

B) shorter

C) unchanged

3. Increasing the mass m of a mass-and-spring simple harmonic oscillator makes its period

A) longer

B) shorter

C) unchanged

4. Increasing the mass m of a simple pendulum makes its period

A) longer

B) shorter

C) unchanged

5. Increasing the length of a simple pendulum makes its period

A) longer

B) shorter

C) unchanged

6. The period of a simple pendulum depends upon its

A) mass

B) amplitude

C) length

7. A mass-and-spring simple harmonic oscillator has maximum potential energy

A) at its equilibrium position

B) where its displacement equals its amplitude

C) half way between equilibrium and amplitude

D) two-thirds of the way between equilibrium and amplitude

8. A simple pendulum has maximum kinetic energy

A) at its equilibrium position

B) where its displacement equals its amplitude

C) half way between equilibrium and amplitude

D) two-thirds of the way between equilibrium and amplitude

9. The amplitude of a simple harmonic oscillator is

A) the time required for one oscillation

B) the number of oscillations per second

C) the energy stored in the oscillations

D) the maximum distance moved from equilibrium

10. The frequency of a certain oscillator is 1000 Hz; its period is

A) 0.1 s

B) 0.01 s

C) 0.001 s

T = 1/f

T = ( 1/1000 ) s

T = 0.001 s

D) 2.345 s

11. The frequency of ordinary household electricity is 60 Hz; its period is

A) 0.167 s

B) 0.0167 s

T = 1/f

T = ( 1/60 ) s

T = 0.0167 s

C) 0.00167 s

D) 120 s

12. There are "signals" of many different frequencies coming into the antenna of your radio. Only the one with a particular frequency is amplified and produces the sound you listen to. This is an example of

A) resonance

B) damping

C) timbre or quality

D) amplitude degeneration

13. Which of the following is a longitudinal wave?

A) wave on a string

B) light

C) sound

D) all of the above

14. A wave has a frequency of 20 Hz and travels 5 m in one second. It has

A) a wave speed of 100 m/s and a wavelength of 4 m.

B) a wave speed of 100 m/s and a wavelength of 1/4 m.

C) a wave speed of 5 m/s and a wavelength of 1/4 m

wave speed = ( frequency ) x ( wavelength )

5 m/s = ( 20 Hz ) ( 1/4 m )

5 m/s = ( 20 1/s ) ( 1/4 m )

5 m/s = ( 20 ) ( 1/4 ) m/s

D) a wave speed of 5 m/s and a wavelength of 4 m

15. A wave has a frequency of 32 Hz and travels 4 m in one second. It has

A) a wave speed of 100 m/s and a wavelength of 128 m.

B) a wave speed of 100 m/s and a wavelength of 1/8 m.

C) a wave speed of 4 m/s and a wavelength of 1/8 m

wave speed = ( frequency ) x ( wavelength )

4 m/s = ( 32 Hz ) ( 1/8 m )

4 m/s = ( 32 1/s ) ( 1/8 m )

4 m/s = ( 32 ) ( 1/8 ) m/s

D) a wave speed of 4 m/s and a wavelength of 8 m

16. A wave has a frequency of 50 Hz and a wavelength of 0.5 m. It has a wave speed of

A) 2.5 m/s

B) 25 m/s

wave speed = ( frequency ) x ( wavelength )

wave speed = ( 50 Hz ) x ( 0.5 m )

wave speed = ( 50 ) x ( 0.5 ) m/s

wave speed = 25 m/s

C) 50 m/s

D) 500 m/s

17. A wave has a frequency of 150 Hz and a wavelength of 0.3 m. It has a wave speed of

A) 2.0 m/s

B) 20 m/s

C) 45 m/s

wave speed = ( frequency ) x ( wavelength )

wave speed = ( 150 Hz ) x ( 0.3 m )

wave speed = ( 150 ) x ( 0.3 ) m/s

wave speed = 45 m/s

D) 50 m/s

18. For standing waves on a string,

A) a node is located at each end [ true ]

B) a whole number times half the wavelength equals the length of the string [ true ]

C) the whole "pattern" of standing waves occurs only for certain frequencies [ true ]

D) all of the above

19. For standing waves on a string, the distance between adjacent nodes is always

A) the length of the string

B) one half the wavelength

C) one wavelength

D) all of the above

20. For standing waves on a string, the distance between adjacent antinodes is always

A) half the length of the string

B) one half the wavelength

C) one wavelength

D) all of the above

21. A bobber on a fishing line oscillates up and down two (2) times per second as waves pass by. The waves have a wavelength of 30 cm. The waves are traveling at

A) 15 cm/s

B) 30 cm/s

C) 60 cm/s

wave speed = ( frequency ) x ( wavelength )

wave speed = ( 2 Hz ) x ( 30 cm )

wave speed = ( 2 ) x ( 30 ) cm/s

wave speed = 60 m/s

D) 100 cm/s

22. If you put your fingertip in a pool of water and repeatedly move it up and down, you will create circular water waves that move out from that point. What will happen to the wavelength of these waves if you move your finger up and down more slowly (or less frequently)?

A) increase

B) remain the same

C) decrease

23. Sound is

A) an electromagnetic wave

B) a polarized wave

C) a longitudinal wave

D) all of the above

24. " Ultrasonic" means

A) lower than the range of human hearing

B) higher than the range of human hearing

C) faster than the speed of sound

D) slower than the speed of sound

25. " Supersonic" means

A) lower than the range of human hearing

B) higher than the range of human hearing

C) faster than the speed of sound

D) slower than the speed of sound

26. Bats and dolphins use echolocation to navigate or the find food or to find their way without relying on sight. The frequencies they use are

A) supersonic

B) infrasonic

C) ultrasonic

D) microsonic

27. The range of human hearing is about

A) 10 Hz to 100 Hz

B) 50 Hz to 500 Hz

C) 50 Hz to 20 000 Hz

D) 1 000 Hz to 100 000 Hz

28. Ella Fitzgerald made commercials for Memorex in which she used her voice to break a wine glass. This is an example of

A) resonance

B) reflected sound

C) ultrasonic frequencies

D) echolocation

29. Beats are heard when two sounds have

A) nearly the same frequencies

B) nearly the same amplitude

C) twice the amplitude

D) exactly twice the frequency

30. The fundamental frequency present in a sound is the

A) sum of all the frequencies mixed together

B) difference between the highest and lowest frequencies present

C) lowest frequency present

D) highest frequency present

31. The fundamental frequency present in a sound determines the

A) quality or timbre

B) amplitude or loudness

C) pitch or note

D) all of the above

32. The "pitch" of a sound is determined by its

A) overtones frequencies

B) harmonics frequencies

C) fundamental frequency

D) resonance frequency

33. The quality or timbre -- the "voice" or the distincitive characteristic -- of a sound is determined by its

A) overtones or harmonics

B) amplitude or loudness

C) attack or decay

D) fundamental frequency

34. Consider a musical note of 440 hertz ("A" on the staff). Two octaves lower is represented by a musical note of

A) 110 Hz
One octave lower than 440 Hz is 220 Hz.

One octave below that is 110 Hz.

B) 440 Hz

C) 660 Hz

D) 880 Hz [ This is one octave above 440 Hz ].

35. Suppose you play a note of a certain pitch on a violin. You can produce a lower-pitched note by

A) shortening the length of the string that vibrates [ This makes a higher pitch ].

B) increasing the tension of the string (tightening the string) [ This makes a higher pitch ].

C) decreasing the linear mass density of the string (using a "lighter" string) [ This makes a higher pitch ].

D) increasing the length of the string that vibrates.

36. When a flute sound is viewed on an oscilloscope, the sound wave is very smooth. This is because

A) the amplitude is always small (flutes are quiet)

B) it has practically no overtones or harmonics

C) its fundamental frequency has a smaller amplitude than its second and third harmonics

D) its harmonics get larger and larger

37. When a piano sound is viewed on an oscilloscope, the sound wave is complex. This is because

A) the amplitude is always large (pianos are loud)

B) it has practically no overtones or harmonics

C) it has many overtones or harmonics

D) its has only even-numbered overtones or harmonics

38. If you apply a force to an oscillator at its natural frequency, you will produce motion

A) at exactly twice that frequency

B) at exactly one-half that frequency

C) with an amplitude that dies out or gets smaller.

D) with large amplitude

39. If a carefully calibrated pendulum were over a very large iron ore deposit, where the acceleration due to gravity is slightly increased, what would happen to the pendulum's period? The pendulum's period would

A) increase

B) stay the same

C) decrease

T = 2 ·

40. Like a transverse wave, a longitudinal wave has a/an

A) amplitude

B) frequency

C) wavelength

D) all of the above

41. For standing waves, antinodes

A) are half a wavelength apart

B) have the greatest amplitude

C) alternate with nodes

D) all of the above

42.  On a string that is 1.0 m long, standing waves may be formed with the following wavelengths:

A) 1.0 m, 2.0 m, 3.0 m

B) 1.0 m, 2.0 m, 4.0 m

C) 3.0 m, 1.5 m, 0.75 m

D) 2.0 m, 1.0 m, 0.5 m

(Drawing a rough sketch will probably help).

43. When two different instruments play the same note or same pitch, their two sounds have the same

A) harmonics

B) overtones

C) amplitudes

D) fundamental frequencies

44. As an oscillator's amplitude decreases, we describe this by saying the oscillator is

A) at resonance

B) driven

C) damped

D) continuous

45. You hear thunder some time after seeing the lightning that caused it because

A) light can not travel through a vacuum

B) light travels faster than sound

C) sound travels faster than light

D) sound can not travel through air

46. Earth receives light from the Sun -- through the vacuum of space -- because light

A) is a longitudinal wave

B) does not require a medium to travel or to "wave"

C) always establishes standing waves

D) is resonant

47. If there were a gigantic explosion on our moon we would not hear it because sound

A) is a transverse wave

B) requires a medium to travel or to "wave"

C) is resonant

D) must be polarized to travel such a great distance

48. Sir Isaac Newton measured the speed of sound

A) extremely accuratly; his measurements were the best at that time

B) using water clocks and an assistant on neighboring hills outside Cambridge

C) to ensure that clocks at sea would keep accurate time

D) to give evidence to his theory of gravitation

E) none of the above

49. The speed of a simple pendulum is zero where the displacement is

A) zero

B) one-half the amplitude

C) the amplitude

D) twice the amplitude

50. The loudness of a sound is associated with its

A) frequency

B) wavelength

C) amplitude

D) period