Physics Exam #2

A grunting porpoise emits sound at 57 Hz . What is the wavelength of this sound in water, where the speed of sound is 1500 m/s?

26 m

A general rule for estimating the distance in kilometers between an observer and a lightning bolt is to count the number of seconds between seeing the lightning and hearing it, and dividing by 4. 5. 3. 2. none of these

3

How many nodes, not including the endpoints, are there in a standing wave that is two wavelengths long?

3

A wave oscillates up and down two complete cycles each second. If the wave travels an average distance of 6 meters in one second, its wavelength is 6 m. 0.5 m. 1 m. 2 m. 3 m.

3 m (6/2)

Radio waves travel at the speed of light, 300,000 km/s. The wavelength of a radio wave received at 100 megahertz is 3.0 m. 300 m. 0.003 m. 30 m. none of these

3.0 m

Three wavelengths long?

5

What is the period, in seconds, that corresponds to each of the following frequencies? 0.2 Hz

5.0 s

The beat frequency produced when a 240 hertz tuning fork and a 246 hertz tuning fork are sounded together is 6 hertz. 240 hertz. 245 hertz. 12 hertz. None of the above choices are correct.

6 hertz

If a turntable's rotational speed is doubled, then the linear speed of a pet hamster sitting on the edge of the record will double. remain the same. halve.

Double

Your pet hamster sits on a record player whose angular speed is constant. If he moves to a point twice as far from the center, then his linear speed halves. remains the same. doubles.

Doubles

How does the lever arm change if you decrease the angle of the force? It decreases. It increases. It stays the same.

It Decreases

How does the lever arm change when you decrease the distance to the nut? It decreases It increases Stays the same

It decreases

If the world's populations moved to the North Pole and the South Pole, would the 24-hour day become longer, shorter, or stay the same? longer shorter stay the same

Shorter

Dan and Sue cycle at the same speed. The tires on Dan's bike are larger in diameter than those on Sue's bike. Which wheels, if either, have the greater rotational speed? Dan's wheels have the greater rotational speed. Sue's wheels have the greater rotational speed. They have the same rotational speed.

Sues's wheels have the greater rotational speed

Do your answers depend on the direction of your push relative to the direction of the wrench handle?

Yes

What about its period? increase does not change decrease

decrease

A railroad locomotive is at rest with its whistle shrieking, then starts moving toward you. Does the frequency of sound that you hear increase, decrease, or stay the same? decreases increases stays the same

increases

How does the force needed to turn the wrench change if you increase the lever arm? It decreases. It stays the same. It increases.

it decreases

Resonance can be looked at as forced vibration with the maximum amount of energy input. least amount of energy input. minimum beat frequency. matching of wave amplitudes. matching of constructive and destructive interference.

least amount of energy input

Consider a string with several rocks tied along its length at equally spaced intervals. You whirl the string overhead so that the rocks follow circular paths. Compared to a rock in the middle of the string, a rock at the outer end moves twice as fast. at the same linear speed. half as fast.

twice as fast

Put a pipe over the end of a wrench when trying to turn a stubborn nut on a bolt, to effectively make the wrench handle twice as long, you'll multiply the torque by two. four. eight.

two

The frequency of a simple pendulum depends on its length. the acceleration due to gravity. its mass. all of these two of these

two of these

To turn a stubborn screw, it is best to use a screwdriver that has a wide handle. long handle. smooth handle. none of these

wide handle

What is the wavelength of a 310-Hz tone in air?

λ = 1.1 m

What is the wavelength of a 31000-Hz ultrasonic wave in air?

λ = 1.1×10^−2 m

Torque = Lever Arm × Force Calculate the torque produced by a 40-N perpendicular force at the end of a 0.15-m-long wrench.

τ = 6.0 Nm

A 340-hertz sound wave travels at 340 m/s in air with a wavelength of 10 m. 1 m. 1000 m. 100 m. None of the above choices are correct.

1m

Can a force produce a torque when there is no lever arm? (y/n)

No

The pendulum with the greatest frequency is the pendulum with the greatest amplitude shortest amplitude. shortest length. shortest period.

shortest period

The object with the highest natural frequency is a small bell. large bell. medium size bell.

small bell

Since each rolling wheel of a railroad train is tapered, the narrow part of the wheel has a tangential speed that is smaller than that of the wide part. greater than that of the wide part. the same as that of the wide part.

smaller than that of the wide part

Which of the following is not a transverse wave? radio sound light all of these none of these

sound

The explanation for refraction must involve a change in wavelength. speed. frequency. All of the above choices are true. None of the above choices are true.

speed

How about the speed of sound in the air between you and the locomotive? increases decreases stays the same

stays the same

Sound travels faster in steel. a vacuum. air. water. Sound travels at about the same speed in all of the above media.

steel

The rotational inertia of your leg is greater when your leg is straight. bent. same either way

straight

The speed of a sound wave in air depends on its wavelength. its frequency. the air temperature. All of the above choices are correct. None of the above choices are correct.

the air temperature

For a system in mechanical equilibrium the resultant forces and torques must be equal. the resultant torques must be zero. the resultant forces and torques must both be zero. the resultant force must be zero.

the resultant forces and torques must both be zero

A Doppler effect occurs when a source of sound moves toward you. at right angles to you. both of these none of these

toward you

A piano tuner knows that a key on the piano is tuned to the frequency of his tuning fork when he strikes them at the same time and the number of beats he hears each second is 2. 4. 1. 0. 3.

0

What is the period, in seconds, that corresponds to each of the following frequencies? 10 Hz

0.10 s

What is the frequency, in hertz, that corresponds to each of the following periods? 5.0 s

0.20 Hz

An object that completes 10 vibrations in 20 seconds has a frequency of 200 hertz. 2 hertz. 0.5 hertz.

0.5 hertz (frequency = vibration/seconds)

A weight suspended from a spring is seen to bob up and down over a distance of 30 cm twice each second. what is its period?

0.50 s

A 1-kg rock is suspended from the tip of a meter stick at the 0-cm mark so that the meter stick balances like a seesaw when the fulcrum is at the 25-cm mark. From this information, what is the mass of the meter stick? 1/4 kg 3/4 kg more than 1 kg 1 kg 1/2 kg

1 kg

The rock and meterstick balance at the 25-cm mark, as shown. The meterstick has a mass of 1.3 kg . What must be the mass of the rock?

1.3 kg

What is the period, in seconds, that corresponds to each of the following frequencies? 60 hz

1.7x10^-2 s

On a balanced seesaw, a boy three times as heavy as his partner sits more than 1/3 the distance from the fulcrum. 1/3 the distance from the fulcrum. less than 1/3 the distance from the fulcrum.

1/3 the distance from the fulcrum

The frequency of the second hand on a clock is 1/60 hertz. 1 hertz. 60 hertz.

1/60 hertz

What is the frequency, in hertz, that corresponds to each of the following periods? 0.10 s

10 Hz

A weight suspended from a spring is seen to bob up and down over a distance of 30 cm twice each second. what is its amplitude?

15 cm

To tighten a bolt, you push with a force of 78 N at the end of a wrench handle that is 0.20 m from the axis of the bolt. What torque are you exerting?

16 Nm (78 x 0.20)

From previous answer: If you move your hand inward to be only 0.10 m from the bolt, find the force

160N

Suppose the circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second when you are riding the bicycle, then your speed will be 3 m/s. 3.14 m/s. 6.28 m/s. 2 m/s. 1 m/s.

2 m/s

A weight suspended from a spring is seen to bob up and down over a distance of 30 cm twice each second. what is its frequency?

2.0 Hz

The approximate range of human hearing is 40 hertz to 40,000 hertz. 10 hertz to 10,000 hertz. 20 hertz to 20,000 hertz. Actually all of these - depends on the hearing ability of the person.

20 hertz to 20,000 hertz

What is the frequency, in hertz, that corresponds to each of the following periods? 1/60 s

60 Hz

The period of the second hand on a clock is 1/60 second. 1 second. 60 seconds. 3600 seconds. 12 hours.

60 seconds

The tapered shape of the parts of the wheels that ride on railroad tracks allows opposite wheels to in effect, vary their diameters. travel at different linear speeds for the same rotational speed. Both A and B are correct.

Both A and B are correct

Centripetal Force: F=mv^2/r Calculate the tension in a horizontal string that whirls a 2.2-kg toy in a circle of radius 2.2 m when it moves at 3.4 m/s on an icy surface.

F= 12N

Calculate the force of friction that keeps a 75-kg person sitting on the edge of a horizontal rotating platform when the person sits 2.0 m from the center of the platform and has a tangential speed of 3.8 m/s .

F= 540N

Angular Momentum = mvr Calculate the angular momentum of the person if the force of friction that keeps a 75-kg person sitting on the edge of a horizontal rotating platform when the person sits 2.1 m from the center of the platform and has a tangential speed of 2.8 m/s .

L = 440 kg⋅m2/s

If the force of friction that keeps a 90-kg person sitting on the edge of a horizontal rotating platform when the person sits 2.2 m from the center of the platform and has a tangential speed of 6.2 m/s , what will be the person's angular momentum?

L= 1200 kg⋅m2/s

We are best at hearing both infrasonic and ultrasonic sounds. infrasonic sound. ultrasonic sound. None of the above choices are true.

None of the above choices are true

Double the frequency of sound and you also double its speed. amplitude. wavelength. all of these none of these

None of these

Which moves faster in m/s on a merry-go-round: a horse on the inside or a horse on the outside near the outer rail? outside horse inside horse Both move at the same speed in m/s.

Outside horse

Caruso is said to have made a crystal chandelier shatter with his voice. This is a demonstration of beats. sound refraction. an echo. resonance. interference.

Resonance

Sound waves can interfere with one another so that no sound results. False True Either true or false, depending on the air temperature.

True

A standing wave occurs when two waves overlap. the speed of the wave is zero or near zero. a wave reflects upon itself. the amplitude of a wave exceeds its wavelength.

a wave reflects upon itself

The famous Leaning Tower of Pisa doesn't topple over because its center of gravity is displaced from its center. relatively low for such a tall building. stabilized by its structure. in the same place as its center of mass. above a place of support.

above a place of support

The Doppler effect is characteristic of sound waves. water waves. light waves. all of the above choices none of the above choices

all of the above choices

For AM radio, the A stands for almost. agony. amplitude. authorized. acceleration.

amplitude

Some of a wave's energy dissipates as heat. In time, this will reduce the wave's speed. amplitude. wavelength. frequency. period.

amplitude

Like a transverse wave, a longitudinal wave has amplitude, wavelength, and speed. amplitude, frequency, and wavelength. wavelength, speed, and frequency. amplitude, frequency, and speed. amplitude, frequency, wavelength, and speed.

amplitude, frequency, wavelength, and speed

A ball rolls down a hill mainly because of its angular acceleration. its angular momentum. an unbalanced torque. a balanced torque. its rotational inertia.

an unbalances torque

The vibrations of a transverse wave move in a direction that changes with speed. along the direction of wave travel. at right angles to the direction of wave travel.

at right angles to the direction of wave travel

The center of gravity of a circular disk of sheet metal is midway between the center and the outside. two-thirds of the way between the center and the outside. at the center of the disk. impossible to predict without knowing the metal density.

at the center of the disk

When the handle of a tuning fork is held solidly against a table, the sound becomes louder and the time that the fork keeps vibrating becomes shorter. becomes longer. remains the same.

becomes shorter

A coin and a ring roll down an incline starting at the same time. The one to reach the bottom first will be the coin. ring. Both reach the bottom at the same time.

coin

A bat flying in a cave emits a sound and receives its echo 0.10 s later. Find its distance from the cave wall

d= 17m

You watch distant Sally Homemaker driving nails into a front porch at a regular rate of 1 stroke per second. You hear the sound of the blows exactly synchronized with the blows you see. And then you hear one more blow after you see the hammering stop. Calculate the distance of sally from you

d= 340m

Imagine a Rip van Winkle type who lives in the mountains. Just before going to sleep, he yells, "WAKE UP", and the sound echoes off the nearest mountain and returns 7.2 hours later. Find the distance between Rip and the imaginary mountain

d= 4400km

How about the wavelength reaching your ear? increases decreases stays the same

decreases

What beat frequencies are possible with tuning forks of frequencies 258, 263, and 267 Hz ?

f1,f2,f3 = 4,5,9 Hz

Inhaling helium increases the pitch of your voice. One reason for this is that sound travels slower in helium than in air. faster in helium than in air. the same speed in helium, but the wavelength is greater.

faster in helium than in air

An oceanic depth-sounding vessel surveys the ocean bottom with ultrasonic waves that travel 1530 m/s in sea-water. The time delay of the echo to the ocean floor and back is 5.75 s . Find the depth of the water directly below the vessel

h= 4400m

A bat chirps as it flies toward a wall. Is the frequency of the echoed chirps it receives higher, lower, or the same as the emitted ones? lower higher the same as the emitted ones

higher

A broom is easier to balance on its end when the heavier end (the brush end) is nearest your hand. highest, farthest from your hand. same either way

highest, farthest from your hand

If a pendulum is shortened, does its frequency increase or decrease? increase decrease does not change

increase

If the Earth rotated more slowly about its axis, your apparent weight would decrease. be zero. stay the same. increase.

increase

The energy of sound in air eventually becomes increased internal energy of the air. cancelled by destructive interference. weaker and weaker until it disappears. cancelled by both destructive and constructive interference.

increased internal energy of the air

Horses that move with the fastest linear speed on a merry-go-round are located near the center. near the outside. anywhere, because they all move at the same speed.

near the outside

An industrial flywheel has a greater rotational inertia when most of its mass is uniformly spread out as in a disk. nearest the axis. nearest the rim.

nearest the rim

A wave travels an average distance of 1 meter in 1 second with a frequency of 1 hertz. Its amplitude is less than 1 meter. more than 1 meter. 1 meter. not enough information to say

not enough information to say

To say that one wave is out of phase with another is to say that the waves are of different wavelengths. of different amplitudes. out of step. of different frequencies. all of these

out of step

Which doesn't belong to the same family? infrasonic waves longitudinal waves ultrasonic waves radio waves shock waves

radio waves

Suppose you are at the center of a large freely-rotating horizontal turntable in a carnival funhouse. As you crawl toward the edge, the angular momentum of you and the turntable remains the same, but the RPMs decrease. decreases. increases. decreases in direct proportion to your decrease in RPMs. none of these

remains the same, but the RPMs decrease

A torque acting on an object tends to produce velocity. a center of gravity. rotation. linear motion. equilibrium.

rotation

When the speed of sound near the ground is greater than it is at higher altitudes, the sound tends to be bent to the right. to the left. upward. downward. None of the above choices are correct.

upward

The source of every sound is something that is a net emitter of energy. vibrating. moving. undergoing simple harmonic motion. accelerating.

vibrating