August 5, 2008
PHY 2053 Discussion
Practice Exam 3 (Chapter 9, 13-14)
1.
Consider two steel rods, A and B. B has three times the area and twice the length of A, so Young’s
modulus for B will be what factor times Young’s modulus for A? (Deformation of Solids-tensile
force)
2.
a. 3.0
b. 0.5
c. 1.5
d. 1.0
The bulk modulus of a material, as a meaningful physical property, is applicable to which of the
following? (Deformation of Solids-bulk force)
a. only solids
b. only liquids
c. only gases
d. solids, liquids and gases
3.
A 15 000-N car on a hydraulic lift rests on a cylinder with a piston of radius 0.20 m. If a connecting
cylinder with a piston of 0.040-m radius is driven by compressed air, what force must be applied to
this smaller piston in order to lift the car? (Pascal’s Principle)
N
4.
a. 600 N
b. 1 500 N
c. 3 000
d. 15 000 N
A piece of aluminum has density 2.70 g/cm3 and mass 775 g. The aluminum is submerged in a
container of oil of density 0.650 g/cm3. A spring balance is attached with string to the piece of
aluminum. What reading will the balance register in grams for the submerged metal? (Buoyant
Force)
5.
a. 960 g
b. 775 g
c. 588 g
d. 190 g
An ideal fluid, of density 0.90×103 kg/m3, flows at 6.0 m/s through a level pipe with radius of 0.50
cm. The pressure in the fluid is 1.3×105 N/m2. This pipe connects to a second level pipe, with radius
of 1.5 cm. Find the speed of flow in the second pipe. (Fluid in Motion)
0.67 m/s
6.
a. 54 m/s
b. 18 m/s
c.
d. 0.33 m/s
A 0.20-kg object, attached to a spring with spring constant k = 10 N/m, is moving on a horizontal
frictionless surface in simple harmonic motion of amplitude of 0.080 m. What is its speed at the
instant when its displacement is 0.040 m? (Simple Harmonic Motion)
49 cm/s
7.
a. 9.8 m/s
b. 4.9 m/s
c.
d. 24.5 cm/s
A mass on a spring vibrates in simple harmonic motion at a frequency of 4.0 Hz and an amplitude of
4.0 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? (SHM as a Function of Time)
0.015 m/s
d. 0.024 m/s
a. zero
b. 0.0065 m/s
c.
8.
By what factor should the length of a simple pendulum be changed if the period of vibration were to
be tripled? (Simple Pendulum)
9.
a. 1/9
b. 0.33
c. 3.0
d. 9.0
A wave travels in a string at 60 m/s. A second string of 20% greater linear density has the same
tension applied as in the first string. What will be the resulting wave speed in the second string?
(Wave Speed in Strings)
a. also 60 m/s
b. 66 m/s
c. 72 m/s
d. 55 m/s
10. Two water waves meet at the same point, one having a displacement above equilibrium of 60 cm and
the other having a displacement above equilibrium of 80 cm. At this moment, what is the resulting
displacement above equilibrium? (Interference of Waves)
a. 140 cm
b. 100 cm
c. 70 cm
d. Information about the amplitudes needs to be given to find the answer.
11. A sound wave in air has a frequency of 500 Hz and a wavelength of 0.68 m. What is the air
a. -18 ˚C
temperature? (Sound Wave)
b. 0 ˚C
c. 15 ˚C
d. 27 ˚C
12. The intensity of sound 20 m from a jet airliner is 120 dB. At what distance from the airplane will the
sound intensity level be a tolerable 100 dB. (Intensity Level of Spherical Waves)
120 m
c. 150 m
a. 90 m
b.
d. 200 m
13. A train station bell gives off a fundamental tone of 500 Hz as the train approaches the station at a
speed of 20 m/s. If the speed of sound in air is 335 m/s, what will be the apparent frequency of the
bell to an observer riding the train? (Doppler Effect)
a. 532 Hz
b. 530 Hz
c. 470 Hz
d.
472 Hz
14. A standing wave is set up in a 2.0-m string fixed at both ends. The string vibrates in 5 distinct
segments when driven by a 120-Hz source. In how many distinct standing wave segments will the
string vibrates if the tension is increased by a factor of 4? (Standing Waves)
a. 3
b. 10
c. 20
d. No standing wave pattern occurs
15. A vibrating guitar string emits a tone simultaneously with one from a 500-Hz tuning fork. If a beat
frequency of 5 Hz results, what is the frequency of vibration of the string? (Beats)
505 Hz
Answers: 1-d
c. 495 Hz
2-d
3-a
a. 2500 Hz
d. Either choice B or C is valid
4-c
5-c
6-c
7-a
8-d
9-d
10-a
11-c
12-d
13-b
14-d
15-d
b.