Final Exam Flashcards
1
Q
Counterclockwise motion, angular displacement is
A
Positive
2
Q
Clockwise motion, angular displacement is
A
Negative
3
Q
A 10 coil spring with constant K. When the spring is cut in half, there are two 5 coil springs. Is the spring constant of each of the shorter springs 1/2k or 2k?
A
2k
-F and +F now applied, double the force, double the k
4
Q
Strain units
A
Strain is unitless
5
Q
Stress is ___. Units of ___.
A
F/A (A=area). F/m^2
6
Q
Angles are often measured in radians. How many degrees are there in one radian?
A
57.3 degrees
7
Q
The SI unit for angular displacement is the radian. In calculations, what is the effect of using the radian?
A
Since the radian is a unitless quantity, there is no effect on other units when multiplying of dividing by the radian.
8
Q
For a given circle, the radian is defined as which one of the following expressions?
A
arc length divided by radius of circle
9
Q
The hand on a stopwatch makes one complete revolution every three seconds. Express the angular speed of this hand in radians per second.
A
2.1 rad/sec
10
Q
A drill bit in a hand drill is turning at 1200 revolutions per minute (1200 rpm). Express this angular speed in radians per second (rad/s).
A
125 rad/sec
11
Q
SI unit angular velocity
A
rad/s
12
Q
The jet engine has angular acceleration of - 2.5 rad/s2. Which one of the following statements is correct concerning this situation?
a) The direction of the angular acceleration is counterclockwise.
b) The direction of the angular velocity must be clockwise.
c) The angular velocity must be decreasing as time passes.
d) If the angular velocity is clockwise, then its magnitude must increase as time passes.
e) If the angular velocity is counterclockwise, then its magnitude must increase as time passes.
A
d) If the angular velocity is clockwise, then its magnitude must increase as time passes.
13
Q
What equations is only valid when the angular measure is expressed in radians?
A
w = (V subscript T)/r
14
Q
Consider the following situation: one of the wheels of a motor cycle is initially rotating at 39 rad/s. The driver then accelerates uniformly at 7.0 rad/s2until the wheels are rotating at 78 rad/s. Which one of the following expressions can be used to find the angular displacement of a wheel during the time its angular speed is increasing?
A
w^2 = wo^2 + 2 alpha*angle
15
Q
A deep space probe is rotating about a fixed axis with a constant angular acceleration. Which one of the following statements concerning the tangential acceleration of any point on the probe is true?
a) The probe’s tangential acceleration is constant in both magnitude and direction.
b) The magnitude of the probe’s tangential acceleration is zero m/s2.
c) The tangential acceleration depends on the angular velocity of the probe.
d) The tangential acceleration is to equal the centripetal acceleration of the probe.
e) The tangential acceleration depends on the change in the probe’s angular velocity.
A
e) The tangential acceleration depends on the change in the probe’s angular velocity.
16
Q
Two points are located on a rigid wheel that is rotating with a decreasing angular velocity about a fixed axis. Point A is located on the rim of the wheel and point B is halfway between the rim and the axis. Which one of the following statements is true concerning this situation?
a) Both points have the same centripetal acceleration.
b) Both points have the same instantaneous angular velocity.
c) Both points have the same tangential acceleration.
d) Each second, point A turns through a greater angle than point B.
e) The angular velocity at point A is greater than that of point B.
A
b) Both points have the same instantaneous angular velocity.
17
Q
As an object rotates, its angular speed increases with time. Complete the following statement: The total acceleration of the object is given by
)the vector sum of the centripetal acceleration and the tangential acceleration.
b) the vector sum of the angular velocity and the tangential acceleration divided by the elapsed time.
c) the angular acceleration.
d) the centripetal acceleration.
e) the tangential acceleration.
A
the vector sum of the centripetal acceleration and the tangential acceleration.
18
Q
Which one of the following statements correctly relates the centripetal acceleration and the angular velocity?
a) The centripetal acceleration is the product of the radius and the square of the angular velocity.
b) The centripetal acceleration is the square of the angular velocity divided by the radius.
c) The centripetal acceleration is the product of the radius and the angular velocity.
d) The centripetal acceleration is the angular velocity divided by the radius.
e) The centripetal acceleration is independent of the angular velocity.
A
The centripetal acceleration is the product of the radius and the square of the angular velocity.
19
Q
A wheel is rolling without slipping along a straight, level road. Which one of the following statements concerning the speed of the center of the wheel is true?
a) A point on the rim is moving at a tangential speed that is equal to the speed at the center of the wheel.
b) A point on the rim is moving at a tangential speed that is one-half the speed at the center of the wheel.
c) A point on the rim is moving at a tangential speed that is two times the speed at the center of the wheel.
d) A point on the rim moves at a speed that is not related to the speed at the center of the wheel.
e) A point on the rim is moving at a tangential speed that varies as the wheel rotates, but the speed at the center of the wheel is constant.
A
A point on the rim is moving at a tangential speed that is equal to the speed at the center of the wheel.
20
Q
The wheels of a NASCAR racer roll without slipping as the car moves in a circular path at constant speed. Which one of the following quantities has a non-zero value and has a constant value in this situation?
a) linear velocity
b) centripetal acceleration
c) angular velocity
d) angular acceleration
e) total acceleration
A
Angular velocity????
21
Q
At the post office, a customer has dropped a coin. The coin is rolling on its side across the floor. Which one of the following statements concerning this situation is true?
a) The tangential velocity is the same for all points on the side of the coin.
b) There is no slipping at the point where the coin touches the floor.
c) The angular acceleration of the coin must be zero m/s2.
d) The tangential velocity is the same for all points on the coin.
e) The linear velocity for all points on the coin is non-zero.
A
No slipping at point where coin touches the floor
22
Q
The wheels of a bicycle roll without slipping on a horizontal road. The bicycle is moving due east at a constant velocity. What is the direction of the angular velocity of the wheels?
a) down
b) west
c) east
d) north
e) south
A
North
23
Q
While putting in a new ceiling, Jake uses a drill to put screws into the drywall. The screws rotate clockwise as they go into the ceiling. What is the direction of the angular velocity of the screw as the drill drives it into the ceiling? Express the direction relative to Jake, who is looking upward at the screw.
a) down
b) up
c) left
d) right
e) forward
A
Up
24
Q
Which one of the following choices is produced when a net torque is applied to a rigid object?
a) a constant acceleration of the object
b) a constant angular velocity of the object
c) a rotational equilibrium of the object
d) a change in the angular velocity of the object
e) a constant angular displacement of the object
A
A change in angular velocity of object
25
A force is applied to a doorknob. This force will be most effective in causing the door to rotate when which of the following is true?
a) The lever arm is parallel to the direction of the force.
b) The lever arm length is zero meters.
c) The direction of the force is at an angle of 45with respect to the door.
d) The direction of the force is at an angle of 90with respect to the door.
e) The lever arm is perpendicular to the door.
The direction of the force is at an angle of 90with respect to the door.
26
Torque units
N*m
27
Which one of the following descriptions indicates that the object is in translational equilibrium?
a) Translational equilibrium occurs only if the object is at rest.
b) Translational equilibrium occurs only if the object is moving with constant acceleration.
c) Translational equilibrium occurs only if the object is at moving with constant velocity.
d) Translational equilibrium occurs if the object is moving with constant velocity or with constant acceleration.
e) Translational equilibrium occurs if the object is at rest or moving with constant velocity.
Translational equilibrium occurs if the object is at rest or moving with constant velocity.
28
```
Consider the drawing. A small disk with a radius rshares an axis with a wheel of radius 4r. An object of mass M1hangs from a rope that is attached and wrapped around the wheel as shown. Another object of mass M2hangs from a rope that is attached and wrapped around the disk as shown. Which one of the following conditions must be true if this system is in equilibrium?
(M1 hangs down further than M2)
a) M1= M2
b) M1< M2
c) M1> M2
```
M1 > M2
29
Complete the following statement: When determining the net torque on a rigid body, only the torques due to
a) internal forces are considered.
b) external forces are considered.
c) forces that are either parallel or perpendicular to the lever arms are considered.
d) forces that form action-reaction pairs as in applying Newton’s third law of motion are considered.
e) internal and external forces are considered.
b) external forces
30
An object, which is considered a rigid body, is in equilibrium. Which one of the following statements is false when determining the forces and torques acting on the object?
a) The linear acceleration or the angular acceleration of the object may not be equal to zero.
b) The location of the rotational axis is arbitrary. Therefore, it can be placed at any point on the object that is convenient.
c) In placing an x-ycoordinate system on the object, the +xdirection is arbitrary and it can be directed toward any direction that is convenient.
d) A free body diagram of the external forces acting on the object is useful in analyzing this situation.
e) The sum of the torques due to external forces must equal zero N m.
The linear acceleration or the angular acceleration of the object may not be equal to zero.
31
A water skier is pulled by a boat traveling with a constant velocity. Which one of the following statements is false concerning this situation?
a) The water skier is in equilibrium.
b) The net acceleration of the skier is zero m/s2.
c) The net force on the skier is zero newtons.
d) There is a net horizontal force on the skier in the direction the boat’s velocity.
e) The net vertical force on the skier is zero newtons.
There is a net horizontal force on the skier in the direction the boat’s velocity.
32
Which one of the following actions will take place if an object in unstable equilibrium is slightly displaced?
a) The object will move in the direction opposite that of the displacement.
b) The object will stop moving as soon as it reaches a place of stable equilibrium.
c) The kinetic energy will decrease.
d) The potential energy will decrease.
The PE decreases
33
Which one of the following statements most accurately describes the center of gravity of an object?
a) It is the point where gravity acts on the object.
b) It is the point on the object where all the weight is concentrated.
c) It is the point from which the torque produced by the weight of the object can be calculated.
d) It must be experimentally determined for all objects.
e) It is the point where all the mass is concentrated.
It is the point from which the torque produced by the weight of the object can be calculated.
34
A flat disk, a solid sphere, and a hollow sphere each have the same mass mand radius r. The three objects are arranged so that an axis of rotation passes through the center of each object. The rotation axis is perpendicular to the plane of the flat disk. Which of the three objects has the largest moment of inertia?
a) The solid sphere and hollow sphere have the same moment of inertia; and it is the largest.
b) The hollow sphere has the largest moment of inertia.
c) The solid sphere has the largest moment of inertia.
d) The flat disk has the largest moment of inertia.
e) The flat disk and hollow sphere have the same moment of inertia; and it is the largest.
b) the hollow sphere has the largest moment of inertia
35
Which one of the following statements concerning the moment of inertia is false?
a) The moment of inertia depends on the angular acceleration of the object as it rotates.
b) The moment of inertia may be expressed in units of kg m2.
c) The moment of inertia depends on the orientation of the rotation axis relative to the particles that make up the object.
d) Of the particles that make up an object, the particle with the smallest mass may contribute the greatest amount to the moment of inertia.
e) The moment of inertia depends on the location of the rotation axis relative to the particles that make up the object.
a) The moment of inertia depends on the angular acceleration of the object as it rotates.
36
An object, which is considered a rigid body, is not in equilibrium. Do both alpha and a have to be greater than zero?
No, Either a or alpha must be > 0 rad or m/sec^2
37
Two solid spheres have the same mass, but one is made from lead and the other from wood. How do the moments of inertia of the two spheres compare?
a) The moment of inertia of the lead sphere is greater than that of the one made of wood.
b) The moment of inertia of the wood sphere is greater than that of the one made of lead.
c) The moment of inertia of the wood sphere is the same as that of the one made of lead.
d) There is no way to compare the spheres without knowing their radii.
The moment of inertia of the wood sphere is greater than that of the one made of lead.
38
An object is rolling, so its motion involves both rotation and translation. Which one of the following statements must be true concerning this situation?
a) The total mechanical energy is equal to the sum of the translational and rotational kinetic energies and the gravitational potential energy of the object.
b) The translational kinetic energy may be equal to zero joules.
c) The gravitational potential energy must be changing as the object rolls.
d) The rotational kinetic energy must be constant as the object rolls.
e) The total mechanical energy is equal to the sum of the translational kinetic energy and the gravitational potential energy of the object.
The total mechanical energy is equal to the sum of the translational and rotational kinetic energies and the gravitational potential energy of the object.
39
A solid cylinder is rolling along a flat, horizontal plane. The center of mass of the cylinder is moving toward the south at constant velocity. Which one of the following statements concerning the translational and rotational kinetic energies of the cylinder is true?
a) The translational kinetic energy is greater than the rotational kinetic energy.
b) The translational kinetic energy is less than the rotational kinetic energy.
c) The translational kinetic energy is equal to the rotational kinetic energy.
d) The sum of the translational and rotational kinetic energies equals the gravitational potential energy of the cylinder.
e) The sum of the translational and rotational kinetic energies equals zero joules.
The translational kinetic energy is greater than the rotational kinetic energy.
40
Which one of the following expressions allows one to calculate the angular momentum for a rigid body about a fixed axis?
I*w
41
A child standing on the edge of a freely spinning merry-go-round moves quickly to the center. Which one of the following statements is necessarily true concerning this event and why?
a) The angular speed of the system decreases because the moment of inertia of the system has decreased.
b) The angular speed of the system increases because the moment of inertia of the system has decreased.
c) The angular speed of the system increases because the moment of inertia of the system has increased.
d) The angular speed of the system decreases because the moment of inertia of the system has increased.
e) The angular speed of the system remains the same because the net torque on the merry-go-round is zero N m.
The angular speed of the system increases because the moment of inertia of the system has decreased.
42
What happens when a spinning ice skater draws in her outstretched arms?
a) Her moment of inertia decreases causing her to slow down.
b) Her angular momentum decreases.
c) The torque that she exerts increases her moment of inertia.
d) Her angular momentum increases.
e) Her moment of inertia decreases causing her to speed up.
Her moment of inertia decreases causing her to speed up.
43
The moment of inertia of a wheel about its axle does not depend on which one of the following properties?
a) the mass of the wheel
b) the diameter of the wheel
c) the angular velocity of the wheel as it rotates
d) the location of the particles that compose the wheel
e) the materials that compose the wheel
c) the angular velocity of the wheel as it rotates
44
A ball moves in a circular path on a horizontal, frictionless surface as shown. It is attached to a light string that passes through a hole in the center of the table. If the string is pulled down, thereby reducing the radius of the path of the ball, the speed of the ball is observed to increase. Which one of the following statements provides an explanation for this increase?
a) When the string is pulled downward, the angular momentum must increase.
b) The total mechanical energy of the ball must remain constant because energy is conserved.
c) The angular momentum of the ball is conserved in this process.
d) The linear momentum of the ball is conserved in this process.
e) This follows from applying Newton’s third law of motion.
c) The angular momentum of the ball is conserved in this process.
45
SI units for angular momentum
kg*m^2/second
46
A hoop rolls without slipping on a horizontal surface and it moves due east at a constant linear speed. What is the direction of its angular momentum?
a) north
b) east
c) south
d) west
e) downward
North
47
There is a restaurant on top of a tall, circular building that is designed to rotate about its center at a constant angular speed. Which one of the following quantities is non-zero and constant for one of the restaurant’s customers seated near a window?
a) linear velocity
b) centripetal acceleration
c) angular momentum
d) angular acceleration
Angular momentum
48
A block is hung vertically at the end of a spring. When the block is displaced and released, it moves in simple harmonic motion. Which one of the following statements is true concerning the block?
a) The maximum acceleration of the block occurs when its velocity is zero.
b) The velocity of the block is never zero m/s.
c) If the velocity of the block is zero m/s, it acceleration is zero m/s2.
d) The maximum velocity occurs when the maximum acceleration occurs.
The maximum acceleration of the block occurs when its velocity is zero.
49
An object is in simple harmonic motion. The rate at which the object oscillates may be described using the period T, the frequency f, and the angular frequency . If the angular frequency decreases, what is the effect on the period and the frequency?
a) The frequency would decrease, but the period would remain the same.
b) The period would increase, but the frequency would remain the same.
c) Both the period and the frequency would decrease.
d) Both the period and the frequency would increase.
e) The period would increase, but the frequency would decrease.
e) The period would increase, but the frequency would decrease.
50
An object in simple harmonic motion is observed to move between a maximum position and a minimum position. The minimum time that elapses between the object being at its maximum position and when it returns to that maximum position is equal to which of the following parameters?
a) frequency
b) angular frequency
c) period
d) amplitude
e) wavelength
c) Period
51
A block is attached to the end of a spring. The block is then displaced from its equilibrium position and released. Subsequently, the block moves back and forth on a frictionless surface without any losses due to friction. Which one of the following statements concerning the total mechanical energy of the block-spring system this situation is true?
a) The total mechanical energy is dependent on the maximum displacement during the motion.
b) The total mechanical energy is at its maximum when the block is at its equilibrium position.
c) The total mechanical energy is constant as the block moves back and forth.
d) The total mechanical energy is only dependent on the spring constant and the mass of the block.
c) The total mechanical energy is constant as the block moves back and forth.
52
A ball is attached to a vertical spring. The ball is initially supported at a height yso that the spring is neither stretched nor compressed. The ball is then released from rest and it falls to a height y hbefore moving upward. Consider the following quantities: translational kinetic energy, gravitational potential energy, elastic potential energy. When the ball was at a height y(h/2), which of the listed quantities has values other than zero joules?
a) translational kinetic energy only
b) gravitational potential energy only
c) elastic potential energy only
d) translational and elastic potential energies only
e) translational kinetic, gravitational potential, and elastic potential energies
e) translational kinetic, gravitational potential, and elastic potential energies
53
A block of mass Mis attached to one end of a spring that has a spring constant k. The other end of the spring is attached to a wall. The block is free to slide on a frictionless floor. The block is displaced from the position where the spring is neither stretched nor compressed and released. It is observed to oscillate with a frequency f. Which one of the following actions would increase the frequency of the motion?
a) Decrease the mass of the block.
b) Increase the length of the spring.
c) Reduce the spring constant.
d) Reduce the distance that the spring is initially stretched.
e) Increase the distance that the spring is initially stretched.
a) decrease the mass of the block
54
Which one of the following statements concerning the total mechanical energy of a harmonic oscillator at a particular point in its motion is true?
a) The mechanical energy depends on the acceleration at that point.
b) The mechanical energy depends on the velocity at that point.
c) The mechanical energy depends on the position of that point.
d) The mechanical energy does not vary during the motion.
e) The mechanical energy is equal to zero joules if the point is the equilibrium point.
d) the mechanical energy does not vary during the motion
55
Under which one of the following conditions does the motion of a simple pendulum approximate simple harmonic motion?
a) when the pendulum swings rapidly
b) when the pendulum swings slowly
c) when the pendulum swings through a small angle
d) when the pendulum swings through a large angle
e) when the length of the pendulum is more than twice the diameter of the bob
c) when the pendulum swings through a small angle
56
Complete the following sentence: In harmonic motion, resonance occurs when
a) the energy in the system is proportional to the square of the motion's amplitude.
b) the driving frequency is the same as the natural frequency of the system.
c) the energy in the system is a minimum.
d) the system is critically damped.
e) the system is overdamped.
b) the driving frequency is the same as the natural frequency of the system.
57
A box that is submerged below the surface of a liquid is observed to have a volume V2, which is smaller than the initial volume V1when the box was in air above the surface. If we wish to determine the “stress” on the box, what additional information is needed?
a) the bulk modulus of the material from which the box is made.
b) the mass of the box.
c) the bulk modulus of the liquid.
d) the shear modulus of the material from which the box is made.
e) the Young's modulus of the material from which the box is made.
a) the bulk modulus of the material from which the box is made.
58
Mike is holding one end of a Slinky. His hand moves up and down and causes a transverse wave to travel along the Slinky away from him. Is the motion of Mike’s hand a wave?
a) Yes, the motion of Mike’s hand is a wave because it moves up and down in periodic motion.
b) Yes, the motion of Mike’s hand is a wave because Mike is transferring energy to the Slinky.
c) No, the motion of Mike’s hand is not a wave because there is no traveling disturbance.
d) No, the motion of Mike’s hand is not a wave because there is no energy traveling along the Slinky.
c) No, the motion of Mike’s hand is not a wave because there is no traveling disturbance.
59
Jimmy and Jenny are floating on a quiet river using giant doughnut-shaped tubes. At one point, they are 5.0 m apart when a speed boat passes. After the boat passes, they begin bobbing up and down at a frequency of 0.25 Hz. Just as Jenny reaches her highest level, Jimmy is at his lowest level. As it happens, Jenny and Jimmy are always within one wavelength. What is the speed of these waves?
a) 1.3 m/s
b) 2.5 m/s
c) 3.8 m/s
d) 5.0 m/s
e) 7.5 m/s
b) 2.5 m/s
60
A longitudinal wave with an amplitude of 0.02 m moves horizontally along a Slinky with a speed of 2 m/s. Which one of the following statements concerning this wave is true?
a) Each particle in the Slinky moves a distance of 2 m each second.
b) Each particle in the Slinky moves a vertical distance of 0.04 m during each period of the wave.
c) Each particle in the Slinky moves a horizontal distance of 0.04 m during each period of the wave.
d) Each particle in the Slinky moves a vertical distance of 0.02 m during each period of the wave.
e) Each particle in the Slinky has a wavelength of 0.04 m.
c) Each particle in the Slinky moves a horizontal distance of 0.04 m during each period of the wave.
61
A sound wave is being emitted from a speaker with a frequency f and an amplitude A. The sound waves travel at a constant speed of 343 m/s in air. Which one of the following actions would reduce the wavelength of the sound waves to one half of their initial value?
a) increase the frequency to 2f
b) increase the amplitude to 2A
c) decrease the frequency to f /4
d) decrease the frequency to f /2
e) decrease the amplitude to A /2
d) decrease frequency to f/2
62
The tension of a guitar string in increased by a factor of 4. How does the speed of a wave on the string increase, if at all?
a) The speed of a wave is reduced to one-fourth the value it had before the increase in tension.
b) The speed of a wave is reduced to one-half the value it had before the increase in tension.
c) The speed of a wave remains the same as before the increase in tension.
d) The speed of a wave is increased to two times the value it had before the increase in tension.
e) The speed of a wave is increased to four times the value it had before the increase in tension.
d) The speed of a wave is increased to two times the value it had before the increase in tension.
63
A climbing rope is hanging from the ceiling in a gymnasium. A student grabs the end of the rope and begins moving it back and forth with a constant amplitude and frequency. A transverse wave moves up the rope. Which of the following statements describing the speed of the wave is true?
a) The speed of the wave decreases as it moves upward.
b) The speed of the wave increases as it moves upward.
c) The speed of the wave is constant as it moves upward.
d) The speed of the wave does not depend on the mass of the rope.
e) The speed of the wave depends on its amplitude.
b) The speed of the wave increases as it moves upward.
64
When a wire is stretched by a force F, the speed of a traveling wave is v. What is the speed of the wave on the wire when the force is doubled to 3F?
a) v
b) 3v
c) 9v
d) v*sqrt(3)
e) v/sqrt(3)
d) v*sqrt(3)
65
A radio station broadcasts its radio signal at a frequency of 101.5 MHz. The signals travel radially outward from a tower at the speed of light. Which one of the following equations represents this wave if t is expressed in seconds and xis expressed in meters?
a) y= 150 sin[(6.377 108)t(2.123)x]
b) y= 150 sin[(637.7)t(2.961)x]
c) y= 150 sin[(6.283 106)t(2.961 103)x]
d) y= 150 sin[(101.5 106)t(2.961)x]
e) y= 150 sin[(101.5 106)t(2.123)x]
a) y= 150 sin[(6.377 x 10^8)t - (2.123)x]
66
The equation for a certain wave is y= 4.0 sin [2pi(2.5t+ 0.14x)] where yand xare measured in meters and tis measured in seconds. What is the magnitude and direction of the velocity of this wave?
a) 1.8 m/s in the +xdirection
b) 1.8 m/s in the -xdirection
c) 18 m/s in the -xdirection
d) 7.2 m/s in the +xdirection
e) 0.35 m/s in the -xdirection
18 m/s in the -x direction
67
Which one of the following statements correctly describes the wave given as this equation: y=3 sin(-4x +2t), where distances are measured in cm and time is measured in ms?
a) The wave is traveling in the +xdirection with an amplitude of 3 cm and a wavelength of pi/2 cm.
b) The wave is traveling in the +xdirection with an amplitude of 4 cm and a wavelength of pi cm.
c) The wave is traveling in the +xdirection with an amplitude of 3 cm and a wavelength of pi cm.
d) The wave is traveling in the +xdirection with an amplitude of 2 cm and a wavelength of pi cm.
e) The wave is traveling in the +xdirection with an amplitude of 6 cm and a wavelength of pi/2 cm.
a) The wave is traveling in the +xdirection with an amplitude of 3 cm and a wavelength of pi/2 cm.
68
Which one of the following correctly describes a wave described by y= 2.0 sin(3.0x - 2.0t) where y and x are measured in meters and tis measured in seconds?
a) The wave is traveling in the +xdirection with a frequency 6piHz and a wavelength 3pim.
b) The wave is traveling in the xdirection with a frequency 4piHz and a wavelength pi/3 m.
c) The wave is traveling in the +xdirection with a frequency pi Hz and a wavelength 3pim.
d) The wave is traveling in the xdirection with a frequency 4pi Hz and a wavelength pi m.
e) The wave is traveling in the +xdirection with a frequency 6piHz and a wavelength pi/3 m.
b) The wave is traveling in the xdirection with a frequency 4piHz and a wavelength pi/3 m.
69
A particle of dust is floating in the air approximately one half meter in front of a speaker. The speaker is then turned on produces a constant pure tone as shown. The sound waves produced by the speaker travel horizontally. Which one of the following statements correctly describes the subsequent motion of the dust particle, if any?
a) The particle of dust will oscillate left and right with a frequency of 226 Hz.
b) The particle of dust will oscillate up and down with a frequency of 226 Hz.
c) The particle of dust will be accelerated toward the right and continue moving in that direction.
d) The particle of dust will move toward the right at constant velocity.
e) The dust particle will remain motionless as it cannot be affected by sound waves.
a) The particle of dust will oscillate left and right with a frequency of 226 Hz.
70
While constructing a rail line in the 1800s, spikes were driven to attach the rails to cross ties with a sledge hammer. Consider the sound that is generated each time the hammer hits the spike. How does the frequency of the sound change, if at al, as the spike is driven into the tie?
a) The frequency of the sound does not change as the spike is driven.
b) The frequency of the sound decreases as the spike is driven.
c) The frequency of the sound increases as the spike is driven.
c) The frequency of the sound increases as the spike is driven.
71
```
In a classroom demonstration, a physics professor breathes in a small amount of helium and begins to talk. The result is that the professor’s normally low, baritone voice sounds quite high pitched. Which one of the following statements best describes this phenomena?
a) The presence of helium changes the speed of sound in the air in the room, causing all sounds to have higher frequencies.
b) The professor played a trick on the class by tightening his vocal cords to produces higher frequencies in his throat and mouth than normal. The helium was only a distraction and had nothing to do with it.
c) The helium significantly alters the vocal chords causing the wavelength of the sounds generated to decrease and thus the frequencies increase.
In a classroom demonstration, a physics professor breathes in a small amount of helium and begins to talk. The result is that the professor’s normally low, baritone voice sounds quite high pitched. Which one of the following statements best describes this phenomena?
a) The presence of helium changes the speed of sound in the air in the room, causing all sounds to have higher frequencies.
b) The professor played a trick on the class by tightening his vocal cords to produces higher frequencies in his throat and mouth than normal. The helium was only a distraction and had nothing to do with it.
c) The helium significantly alters the vocal chords causing the wavelength of the sounds generated to decrease and thus the frequencies increase.
d) The wavelength of the sound generated in the professor’s throat and mouth is only changed slightly, but since the speed of sound in helium is approximately 2.5 times larger than in air, therefore the frequencies generated are about 2.5 times higher.
```
d) The wavelength of the sound generated in the professor’s throat and mouth is only changed slightly, but since the speed of sound in helium is approximately 2.5 times larger than in air, therefore the frequencies generated are about 2.5 times higher.
72
Ethanol has a density of 659 kg/m^3. If the speed of sound in ethanol is 1162 m/s, what is its adiabatic bulk modulus?
a) 1.7 x10^8N/m^2
b) 2.2 x10^8N/m^2
c) 7.7 x10^8N/m^2
d) 8.9 x10^8N/m^2
e) 6.1 x10^9N/m^2
d) 8.9 x10^8N/m^2
73
Natalie is a distance din front of a speaker emitting sound waves. She then moves to a position that is a distance 2din front of the speaker. By what percentage does the sound intensity decrease for Natalie between the two positions?
a) 10 %
b) 25 %
c) 50 %
d) 75%
e) The sound intensity remains constant because it is not dependent on the distance.
d) 75%
74
A bell is ringing inside of a sealed glass jar that is connected to a vacuum pump. Initially, the jar is filled with air at atmospheric pressure. What does one hear as the air is slowly removed from the jar by the pump?
a) The sound intensity gradually increases.
b) The sound intensity gradually decreases.
c) The sound intensity of the bell does not change.
d) The frequency of the sound gradually increases.
e) The frequency of the sound gradually decreases.
b) the sound intensity gradually decreases
75
A sound level meter is used measure the sound intensity level. A sound level meter is placed an equal distance in front of two speakers, one to the left and one to the right. A signal of constant frequency may be sent to each of the speakers independently or at the same time. When either the left speaker is turned on or the right speaker is turned on, the sound level meter reads 90.0 dB. What will the sound level meter read when both speakers are turned on at the same time?
a) 90.0 dB
b) 93.0 dB
c) 96.0 dB
d) 100.0 dB
e) 180.0 dB
b) 93 dB
76
A sound level meter is used measure the sound intensity level. A sound level meter is placed an equal distance in front of two speakers, one to the left and one to the right. A signal of constant frequency, but differing amplitude, is sent to each speaker independently. When the left speaker is turned on the sound level meter reads 85 dB. When the right speaker is turned on the sound level meter reads 65 dB. What will the sound level meter read when both speakers are turned on at the same time?
a) about 85 dB
b) about 65 dB
c) about 150 dB
d) about 75 dB
e) about 113 dB
a) about 85 dB
77
Software is used to amplify a digital sound file on a computer by 20 dB. By what factor has the intensity of the sound been increased as compared to the original sound file?
a) 2
b) 5
c) 10
d) 20
e) 100
e) 100
78
Two stationary observers, Keisha and Trina, are listening to the sound from a moving source. The sound from the source has a constant frequency fSand constant amplitude. As the source moves, Trina hears two different frequencies f1and f2, where f1> fSand f2< fS. Keisha, who is not moving with the source, only hears one frequency, f. Which one of the following statements best explains this situation?.
a) The source is moving very slowly relative to Keisha, but fast relative to Trina.
b) The source is moving along a parabolic path and Keisha is at the origin of the parabola. Trina is inside the parabola.
c) Keisha is standing at a location where the wind is blowing in such a way as to remove the Doppler effect, while Trina is standing in a location where there is no wind.
d) The source is moving along a circle and Keisha is at the center of the circle. Trina is outside the circle.
e) The source is moving along an ellipse and Keisha is at one of the two foci of the ellipse. Trina is outside the ellipse.
d) The source is moving along a circle and Keisha is at the center of the circle. Trina is outside the circle.
79
A child is swinging back and forth with a constant period and amplitude. Somewhere in front of the child, a stationary horn is emitting a constant tone of frequency fS. Five points are labeled in the drawing to indicate positions along the arc as the child swings. At which position(s) will the child hear the lowest frequency for the sound from the whistle?
short distance while moving backwards away from sound
80
Hydrogen atoms in a distant galaxy are observed to emit light that is shifted to lower frequencies with respect to hydrogen atoms here on Earth. Astronomers use this information to determine the relative velocity of the galaxy with respect to the Earth by observing how light emitted by atoms is Doppler shifted. For the hydrogen atoms mentioned, how are the wavelengths of light affected by the relative motion, if at all?
a) The wavelengths would be unchanged, only the frequencies are shifted.
b) The wavelengths of light would be longer than those observed on Earth.
c) The wavelengths of light would be shorter than those observed on Earth.
b) The wavelengths of light would be longer than those observed on earth
