Excursions in Physics

Third Hour Exam

May 27, 1999

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For every question, also consider as a possible answer

E) none of the above

Possibly useful information:

v = x / tp = m v T = 2

a = v / tPE = m g h T = 2

v = v_i+ a t PE = (¹/₂) k x²v =

x = x_i + v_i t + (¹/₂) a t²KE = (¹/₂) m v²v=(wavelength) x (frequency)

v = r F = k x L = (n) x (half wavelength)

F = m a E_i = E_f

F₁₂ = - F₂₁p_i = p_f

w = mg F = p / t

g = 9.8 m/s² 10 m/s²

For every question, also consider as a possible answer

E) none of the above

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

A) longer
B) shorter
C) unchanged

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

A) at its equilibrium position
B) when its displacement equals its amplitude
C) half way between equilibrium and amplitude
D) two-thirds of the way between equilibrium and amplitude

5. A mass-and spring simple harmonic oscillator has maximum kinetic energy

A) at its equilibrium position
B) when its displacement equals its amplitude
C) half way between equilibrium and amplitude
D) two-thirds of the way between equilibrium and amplitude

6. The amplitude of a simple harmonic oscillator is

A) the time required for one oscillation
B) the number of oscillators per second
C) the energy stored in the oscillations
D) the maximum distance moved from equilibrium

7. The frequency of a certain oscillator is 100 Hz; its period is

A) 0.1 s
B) 0.01s; T = 1/f = 1/100 = 0.01 s
C) 0.001 s
D) 0.0001 s

8. 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

9. Which of the following is a longitudinal wave?

A) wave on a string
B) light
C) sound
D) all of the above

10. 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
v = (freq) x (wavelength)
wavelength = v / freq = (5 m/s) / (20 Hz) = (1/4) m
D) a wave speed of 5 m and a wavelength of 4 m

11. 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
v = (freq) x (wavelength)
wavelength = v / freq = (4 m/s) / (32 Hz) = (1/8) m
D) a wave speed of 4 m and a wavelength of 8 m

12. 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) 10 m/s
C) 25 m/s
v = (freq) x (wavelength)
v = (50 Hz) (0.5 m) = 25 m/s
D) 100 m/s

13. For standing waves on a string,

A) a node is located at each end
B) a whole number times half the wavelength equals the length of the string
C) the whole "pattern" of standing waves occurs only for certain frequencies
D) all of the above

14. 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

15. 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

16. 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 25 cm. The waves are traveling at

A) 12.5 cm/s
B) 25 cm/s
C) 50 cm/s
v = (freq) x (wavelength)
v = (2 Hz) (25 cm) = 50 m/s
D) 100 cm/s

17. 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
v = (wavelength) x (frequency)
A decrease in frequency means an increase in wavelength.
B) remain the same
C) decrease

18. Sound is

A) an electromagnetic wave

light is an electromagnetic wave
radio and television and X-rays are also electromagnetic wave

B) a polarized wave

only transverse waves can be polarized
longitudinal waves can not be polarized

C) a longitudinal wave
D) all of the above

19. "Infrasonic" 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

20. 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

Both bats and dolphins use ultrasound with frequencies of about 50 kHz and above.

D) microsonic

21. 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

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

A) echolocation
B) reflected sound
C) ultrasonic frequencies
D) resonance

23. Beats are heard when two sounds have

A) nearly the same amplitude
B) nearly the same frequencies
C) twice the amplitude
D) exactly twice the wavelength

24. 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

25. The fundamental frequency present in a sound determines the

A) quality or timbre
B) amplitude
C) pitch or note
D) all of the above

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

A) overtones frequencies
B) harmonics frequencies
C) fundamental frequency
D) resonance frequencies

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

A) overtones or harmonics
B) amplitude or loudness
C) attack or decay
D) frequency

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

A) 110 Hz
B) 440 Hz
C) 660 Hz
D) 880 Hz

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

A) shortening the length of the string that is allowed to vibrate
B) decreasing the tension of the string (loosening the string)
C) increasing the linear mass density of the string (using a "heavier" string)
D) lengthening the part of the string that vibrates.

30. 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.

31. When a trumpet sound is viewed on an oscilloscope, the sound wave is very complex. This is because

A) the amplitude is always large (trumpets are loud)
B) it has practically no overtones or harmonics
C) it has many overtones or harmonics
D) it has only even-numbered overtones or harmonics.

32. Increasing the mass of a simple pendulum makes its period

A) longer
B) shorter
C) unchanged

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

A) longer
B) shorter
C) unchanged

34. The period of a simple pendulum depends upon its

A) mass
B) amplitude
C) length

35. Ordinary household electricity is alternating current with a frequency of 60 Hz. Its period is

A) 60 cycles per second
B) 120 cycles per second
C) 0.0333 s
D) 0.0167 s; T = 1/f = 1/(60 Hz) = 1/(60 cyc/s) = (1/60) s = 0.0167 s

36. 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

37. If a carefully calibrated pendulum were over a very large oil deposit, where the acceleration due to gravity is slightly decreased, what would happen to the pendulum's period?

A) increase; T = 2
B) stay the same
C) decrease

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

A) amplitude
B) frequency
C) wavelength
D) all of the above

39. For standing waves, antinodes

A) are half a wavelength apart
B) have the greatest amplitude
C) alternate with nodes
D) all of the above

40. 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

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