Physics 2 Exam 1

A 10-kg piece of aluminum sits at the bottom of a lake, right next to a 10-kg piece of lead, which is much denser than aluminum. Which one has the greater buoyant force on it?

the aluminum

Fluid flows at 2.0 m/s through a pipe of diameter 3.0 cm. What is the volume flow rate of the fluid?

1.4 × 10^-3 m^3/s

What is the length of the shortest pipe closed on one end and open at the other end that will have a fundamental frequency of 0.060 kHz on a day when the speed of sound is 340 m/s?

1.42 m

Glycerin, with a viscosity of 1.5 N Â s/m2, is flowing with an average speed of 1.2 m/s through a tube that has a radius of 5.0 mm and is 25 cm long. What is the drop in pressure over the length of this pipe?

140 kPa

A train is traveling away from you at 120 km/h. It blows its whistle, and you hear a tone of 0.400 kHz. Take the speed of sound to be 340 m/s. What frequency does the whistle actually produce?

439 Hz

A crane lifts a steel submarine of density 7800 kg/m3 and mass 20,000 kg. What is the tension in the lifting cable (a) when the submarine is submerged in water of density 1000 kg/m3 , and (b) when it is entirely out of the water?

(a) 1.7 × 10^5 N (b) 2.0 × 10^5 N

A tsunami, an ocean wave generated by an earthquake, propagates along the open ocean at 700 km/hr and has a wavelength of 750 km. What is the frequency of the waves in such a tsunami?

0.00026 Hz

Motor oil, with a viscosity of 0.25 N Â s/m2, is flowing through a tube that has a radius of 5.0 mm and is 25 cm long. The drop in pressure is 300 kPa. What is the volume of oil flowing through the tube per second?

0.0012 m3 /s

A fluid is flowing with an average speed of 1.5 m/s through a tube that has a radius of 2.0 mm and is 18 cm long. The drop in pressure is 967 Pa. What is the viscosity of the fluid?

0.0018 N* s/m2

Ideal incompressible water flows through a horizontal pipe of cross-sectional area 10.0 cm2 at a pressure of 0.250 atm with a volume flow rate of 1.00 × 10-3 m3 /s. At a valve, the effective cross-sectional area of the pipe is reduced to 5.00 cm2 . What is the pressure at the valve?

0.235 atm

Water flows through a horizontal pipe of cross-sectional area 10.0 cm2 at a pressure of 0.250 atm with a flow rate is 1.00 L/s. At a valve, the effective cross-sectional area of the pipe is reduced to 5.00 cm2 . What is the pressure at the valve? The density of water is 1000 kg/m3 , and treat it as an ideal incompressible fluid.

0.235 atm

A 4.0-g string is 0.36 m long and is under tension. The string vibrates at 500 Hz in its third harmonic. What is the wavelength of the standing wave in the string?

0.24 m

You are moving at 120 km/h toward a stationary train. The train blows its 0.400-kHz whistle. Take the speed of sound to be 340 m/s. What frequency do you hear?

439 Hz

Two in-phase loudspeakers are placed along a wall and are separated by a distance of 4.00 m. They emit sound with a frequency of 514 Hz. A person is standing away from the wall, in front of one of the loudspeakers. What is the closest distance from the wall the person can stand and hear destructive interference? The speed of sound in air is 343 m/s.

0.34 m

Two in-phase loudspeakers are 3.0 m apart. They emit sound with a frequency of 490 Hz. A microphone is placed half-way between the speakers and then moved along the line joining the two speakers until the first point of constructive interference is found. At what distance from that midpoint is that first point? The speed of sound in air is 343 m/s.

0.35 m

What is the frequency of the wave shown in the figure?

0.5 Hz.

A hot air balloon along with its cargo has a mass of 4.0 × 105 kg, and it holds 7.0 × 105 m3 of hot air. It is floating at a constant height in air with a density of 1.29 kg/m3. What is the density of the hot air in the balloon?

0.72 kg/m3

A rectangular wooden block measures 10.0 cm × 4.00 cm × 2.00 cm. When the block is placed in water, it floats horizontally, with its bottom face 1.65 cm below the surface. What is the density of the wood? The density of water is 1.00 g/cm3.

0.825 g/cm3

Motor oil, with a viscosity of 0.25 N Â s/m2, is flowing through a tube that has a radius of 3.0 mm and is 1.0 m long. The drop in pressure over the length of the tube is 200 kPa. What is the average speed of the oil?

0.90 m/s

The Aswan High Dam on the Nile River in Egypt is 111 m high. What is the gauge pressure in the water at the foot of the dam? The density of water is 1000 kg/m3 .

1.09x10^6 Pa

The Tonga Trench in the Pacific Ocean is 36,000 feet deep. Assuming that sea water has an average density of 1.04 g/cm3 , calculate the absolute (total) pressure at the bottom of the trench in atmospheres. (1.00 in = 2.54 cm, 1.00 atm = 1.01 × 105 Pa)

1.1 × 10^3 atm

The deepest point of the Pacific Ocean is 11,033 m, in the Mariana Trench. What is the gauge pressure in the water at that point? The density of seawater is 1025 kg/m3 .

1.11 × 10^8 Pa

A plastic block of dimensions 2.00 cm × 3.00 cm × 4.00 cm has a mass of 30.0 g. What is its density?

1.25 g/cm3

One of the harmonics of a column of air in a tube that is open at one end and closed at the other has a frequency of 448 Hz, and the next higher harmonic has a frequency of 576 Hz. How long is the tube? The speed of sound in air is 343 m/s

1.34 m

Two motors in a factory are running at slightly different rates. One runs at 825.0 rpm and the other at 786.0 rpm. You hear the sound intensity increase and then decrease periodically due to wave interference. How long does it take between successive instances of the sound intensity increasing?

1.54 s

Two stereo speakers mounted 4.52 m apart on a wall emit identical sound waves. You are standing at the opposite wall of the room at a point directly between the two speakers. You walk 2.11 m parallel to the wall, to a location where you first notice that the sound intensity is essentially zero. If the wall along which you are walking is 10.7 m from the wall with the speakers, what is the wavelength of the sound waves? The walls are cushioned to absorb sound reflections.

1.71 m

A 12,000-N car is raised using a hydraulic lift, which consists of a U-tube with arms of unequal areas, filled with oil with a density of 800 kg/m3 and capped at both ends with tight-fitting pistons. The wider arm of the U-tube has a radius of 18.0 cm and the narrower arm has a radius of 5.00 cm. The car rests on the piston on the wider arm of the U-tube. The pistons are initially at the same level. What is the force that must be applied to the smaller piston in order to lift the car after it has been raised 1.20 m? For purposes of this problem, neglect the weight of the pistons.

1.96 kN

A block of metal weighs 40 N in air and 30 N in water. What is the buoyant force on the block due to the water? The density of water is 1000 kg/m3.

10 N

A violin with string length 32 cm and string density 1.5 g/cm resonates in its fundamental with the first overtone of a 2.0-m organ pipe with one end closed and one end open. What is the tension in the string if the speed of sound in air is 344 m/s?

1000 N

A 500-N weight sits on the small piston of a hydraulic machine. The small piston has an area of 2.0 cm2 . If the large piston has an area of 40 cm2 , how much weight can the large piston support? Assume the pistons each have negligible weight

10000 N

What is the ratio of the intensities of two sounds with intensity levels of 70 dB and 40 dB?

1000:1

A person who weighs 550 N empties her lungs as much as possible and is then completely immersed in water of density 1000 kg/m3 while suspended from a harness. Her apparent weight is now 21.2 N. What is her density?

1040 kg/m3

What is the intensity of a 70-dB sound? The threshold of human hearing is 1.0 × 10-12 W/m2

10^-5 W/m2

If a ship has a mass of 10 million kilograms, what volume of fresh water must it displace in order to float? The density of water is 1000 kg/m3 .

10^4 m^3

A 25-g string is stretched with a tension of 43 N between two fixed points 12 m apart. What is the frequency of the second harmonic?

12 Hz

A brick weighs 50.0 N, and measures 30.0 cm × 10.0 cm × 4.00 cm. What is the maximum pressure it can exert on a horizontal surface due to its weight?

12.5 kPa

When a container of water is placed on a laboratory scale, the scale reads 120 g. Now a 20-g piece of copper (of density 8.9 g/cm3 ) is suspended from a thread and lowered into the water, not touching the bottom of the container. What will the scale now read? The density of water is 1.0 g/cm3 .

122 g

Water flows out of a large reservoir through an open pipe, as shown in the figure. What is the speed of the water as it comes out of the pipe?

13 m/s

What is the wave speed in a brass wire with a radius of 0.500 mm stretched with a tension of 125 N? The density of brass is 8.60 × 103 kg/m3.

136 m/s

A string that is 0.15 m long and fixed at both ends is vibrating in its n = 5 harmonic. The sound from this string excites a pipe that is 0.82 m long and open at both ends into its second overtone resonance. What is the distance between a node and an adjacent antinode, in the string? The speed of sound in air is 345 m/s.

15 mm

If a guitar string has a fundamental frequency of 500 Hz, which one of the following frequencies can set the string into resonant vibration?

1500 Hz

Two horizontal pipes are the same length, but pipe B has twice the diameter of pipe A. Water undergoes viscous flow in both pipes, subject to the same pressure difference across the lengths of the pipes. If the flow rate in pipe A is Q = ǻV ǻt , what is the flow rate in pipe B?

16Q

Two loudspeakers placed 6.00 m apart are driven in phase by an audio oscillator having a frequency range from 1595 Hz to 2158 Hz. A point P is located 4.70 m from one loudspeaker and 3.60 m from the other speaker. The speed of sound in the room is 344 m/s. At what frequency (or frequencies) of the oscillator does the sound reaching point P interfere destructively? (There could be more than one correct choice.)

1720 Hz, 2030 Hz

A person weighing 900 N is standing on snowshoes. Each snowshoe has area 2500 cm2 and has negligible weight. What pressure does this person's weight exert on the snow?

1800 N/m2

What is the frequency of the fundamental mode of vibration of a steel piano wire stretched to a tension of 440 N? The wire is 0.600 m long and has a mass of 5.60 g.

181 Hz

A compressed gas with a total mass of 107 kg is stored in a spherical container having a radius of 0.521 m. What is the density of the compressed gas?

181 kg/m3

A crane lifts a 2500-kg beam at a steady rate of 15 cm/s using a steel cable whose mass per unit length is 0.65 kg/m. What is the speed of transverse waves on this cable?

190 m/s

A solid sphere of mass 8.6 kg, made of metal whose density is 3400 kg/m3, hangs by a cord. When the sphere is immersed in a liquid of unknown density, the tension in the cord is 38 N. The density of the liquid is closest to which one of the following values?

1900 kg/m3

How many grams of ethanol (density 0.80 g/cm3 ) should be added to 5.0 g of chloroform (density 1.5 g/cm3 ) if the resulting mixture is to have a density of 1.2 g/cm3 ? Assume that the fluids do not change their volumes when they are mixed.

2.0 g

Calculate the pressure exerted on the ground due to the weight of a 79-kg person standing on one foot. if the bottom of the person's foot is 13 cm wide and 28 cm long.

2.1 × 10^4 Pa

In a hydraulic garage lift, the small piston has a radius of 5.0 cm and the large piston has a radius of 15 cm. What force must be applied on the small piston in order to lift a car weighing 20,000 N on the large piston? Assume the pistons each have negligible weight.

2.2 × 10^3 N

Find the speed of an ocean wave whose displacement is given by the equation y = 3.7 cos(2.2x - 5.6t) where x and y are in meters and t is in seconds.

2.5 m/s

Ideal incompressible water is flowing in a drainage channel of rectangular cross-section. At one point, the width of the channel is 12 m, the depth of water is 6.0 m, and the speed of the flow is 2.5 m/s. At a point downstream, the width has narrowed to 9.0 m, and the depth of water is 8.0 m. What is the speed of the flow at the second point?

2.5 m/s

A rectangular box of negligible mass measures 5.0 m long, 1.0 m wide, and 0.50 m high. How many kilograms of mass can be loaded onto the box before it sinks in a lake having water of density 1000 kg/m3 ?

2.5 × 10^3 kg

The weight of a 1200-kg car is supported equally by the four tires, which are inflated to the same gauge pressure. What gauge pressure is required so the area of contact of each tire with the road is 100 cm2 ?

2.9 × 10^5 Pa

A 200-N object floats with three-fourths of its volume beneath the surface of the water. What is the buoyant force on the object? The density of water is 1000 kg/m3 .

200 N

An earthquake generates three kinds of waves: surface waves (L-waves), which are the slowest and weakest, shear (S) waves, which are transverse waves and carry most of the energy, and pressure (P) waves, which are longitudinal waves and are the fastest. The speed of P waves is approximately 7 km/s, and that of S waves is about 4 km/s. People do not generally feel the P waves, but animals seem to be sensitive to them. If a person reports that her dog started barking 20 seconds "before the earthquake," then approximately how far was the origin of the earthquake?

200 km

An object floats with half its volume beneath the surface of the water. The weight of the displaced water is 2000 N. What is the weight of the object? The density of water is 1000 kg/m3 .

2000 N

A container has a vertical tube, whose inner radius is 24.00 mm, connected to it at its side, as shown in the figure. An unknown liquid reaches level A in the container and level B in the tube-level A being 5.0 cm higher than level B. The liquid supports a 20-cm high column of oil, between levels B and C, whose density is 570 kg/m3. The mass of the oil is closest to

210.

The bathyscaphe Trieste consists of a thin-walled but very strong cylindrical hull, 15.2 m long and 3.66 m in diameter, filled with gasoline with a density of 880 kg/m3 to make it buoyant. If it is totally submerged in seawater with a density of 1025 kg/m3 and neither rising nor sinking, what is the weight of the Trieste craft?

227 kN

The sound from the whistle of a truck moving at 17.0 m/s toward a cliff reflects from the cliff and is heard by the driver of the truck. When it is parked at the side of the road, the whistle from the truck produces sound of frequency 2.267 kHz. As observed by the driver of the truck, what is the change in frequency the sound from the whistle due to the reflection? The speed of sound is 343 m/s.

236 Hz

A 4.0-g string is 0.39 m long and is under tension. The string vibrates at 600 Hz in its third harmonic. What is the tension in this string?

250 N

A string that is 2.0 meters long is fixed at both ends and tightened until the wave speed is 18 m/s. What is the frequency of the standing wave shown in the figure?

27 Hz

Two in-phase loudspeakers that emit sound with the same frequency are placed along a wall and are separated by a distance of 8.00 m. A person is standing 12.0 m away from the wall, equidistant from the loudspeakers. When the person moves 3.00 m parallel to the wall, she experiences destructive interference for the second time. What is the frequency of the sound? The speed of sound in air is 343 m/s.

278 Hz

The intensity at a distance of 6.0 m from a source that is radiating equally in all directions is 6.0 × 10-10 W/m2. What is the intensity level in dB? The threshold of human hearing is 1.0 × 10-12 W/m2.

28 dB

Consider a pipe of length L that is open at both ends. What are the wavelengths of the three lowest-pitch tones produced by this pipe?

2L, L, 2L/3

Two horizontal pipes have the same diameter, but pipe B is twice as long as pipe A. Water undergoes viscous flow in both pipes, subject to the same pressure difference across the lengths of the pipes. If the flow rate in pipe B is Q = ǻV ǻt what is the flow rate in pipe A?

2Q

An ideal incompressible fluid flows at 12 m/s in a horizontal pipe. If the pipe widens to twice its original radius, what is the flow speed in the wider section?

3.0 m/s

A 100-kg person sits on a 5-kg bicycle. The total weight is borne equally by the two wheels of the bicycle. The tires are 2.0 cm wide and are inflated to a gauge pressure of 8.0 × 105 Pa. What length of each tire is in contact with the ground?

3.2 cm

Water flows out of a large reservoir through 5.0-cm diameter pipe. The pipe connects to a 3.0-cm diameter pipe that is open to the atmosphere, as shown in the figure. What is the speed of the water in the 5.0-cm pipe? Treat the water as an ideal incompressible fluid.

3.2 m/s

A certain glass window reduces the intensity level of the sound from 72 dB to 47 dB. By what factor is the acoustic power reduced by this glass window?

3.2 × 10^-3

A bat emits a sound at a frequency of 39.0 kHz as it approaches a wall. The bat detects beats with a frequency of 827 Hz between the sound it emits and the echo bouncing from the wall. What is the speed of the bat if the speed of sound in air is 343 m/s?

3.6 m/s

Calculate the light intensity 1.45 m from a light bulb that radiates 100 W equally in all directions.

3.78 W/m2

A water tank is filled to a depth of 10 m, and the bottom of the tank is 20 m above ground. A water-filled hose that is 2.0 cm in diameter extends from the bottom of the tank to the ground, but no water is flowing in this hose. The water pressure at ground level in the hose is closest to which of the following values? The density of water is 1000 kg/m3 .

3.9 × 10^5 N/m^2

If the frequency of a violin string is to be increased by 20%, what change in tension must be applied?

44%

A stretched string is observed to have four equal segments in a standing wave driven at a frequency of 480 Hz. What driving frequency will set up a standing wave with five equal segments?

600 Hz

A pressurized cylindrical tank, 5.0 m in diameter, contains water that emerges from the pipe at point C with a speed of 84 m/s, as shown in the figure. Point A is 10 m above point B and point C is 3.0 m above point B. The area of the pipe at point B is 0.080 m2 and the pipe narrows to an area of 0.070 m2 at point C. Assume that the water is an ideal fluid in laminar flow. The density of water is 1000 kg/m3 . The rate at which the water level is falling in the tank is closest to

300 mm/s.

Under standard conditions, the density of air is 1.29 kg/m3. What is the mass of the air inside a room measuring 4.0 m × 3.0 m × 2.0 m?

31 kg

A 4.0-kg cylinder of solid iron is supported by a string while submerged in water. What is the tension in the string? The density of iron is 7860 kg/m3 and that of water is 1000 kg/m3

34 N

A 10-gram wire that is 6.0 m long is under tension. When a transverse wave of frequency 280 Hz travels along the wire, its wavelength is 0.60 m,and its amplitude is 8.4 mm. How much time does it take for a crest of the transverse wave to travel the length of the wire?

36 ms

Two steel wires are stretched with the same tension. The first wire has a diameter of 0.610 mm and the second wire has a diameter of 0.910 mm. If the speed of waves traveling along the first wire is 54.0 m/s, what is the speed of waves traveling along the second wire?

36.2 m/s

A container has a vertical tube, whose inner radius is 20.00 mm, connected to it at its side, as shown in the figure. An unknown liquid reaches level A in the container and level B in the tube-level A being 5.0 cm higher than level B. The liquid supports a 20-cm high column of oil, between levels B and C, whose density is 900 kg/m3. The density of the unknown liquid is closest to

3600 kg/m3.

A cylindrical rod of length 12 cm and diameter 2.0 cm will just barely float in water of density 1000 kg/m3 . What is its mass?

38 g

A 0.13-m string, fixed at both ends and vibrating in its n = 4 harmonic, excites a pipe that is 0.88 m long and open at both ends, into its second overtone resonance. What is the speed of transverse waves on the string? The speed of sound in air is 345 m/s.

38 m/s

A standing wave is oscillating at 950 Hz on a string, as shown in the figure. What is the wave speed?

380 m/s

Ideal incompressible fluid flows through a 4.0-cm-diameter pipe at 1.0 m/s. There is a 2.0 cm diameter constriction in the line. What is the speed of the fluid in this constriction?

4.0 m/s

A polar bear of mass 200 kg stands on an ice floe that is a uniform 1.0 m thick. What is the minimum area of the floe that will just support the bear in saltwater of density 1030 kg/m3 ? The density of ice is 980 kg/m3 .

4.0 m2

The average intensity of sunlight impinging on Earth is measured to be about 1.4 kW/m2. What is the power of sunlight emitted by the sun? (Earth-Sun distance = 1.5 × 108 km, Earth radius = 6.4 × 103 km)

4.0 × 10^26 W

One of the dangers of tornados and hurricanes is the rapid drop in air pressure that is associated with such storms. Assume that the air pressure inside of a sealed house is 1.02 atm when a hurricane hits. The hurricane rapidly decreases the external air pressure to 0.910 atm. What net outward force is exerted on a square window of the house that is 2.03 m on each side? (1.00 atm = 1.01 × 105 Pa)

4.59 × 10^4 N

The lowest tone to resonate in a pipe of length L that is closed at one end but open at the other end is 200 Hz. Which one of the following frequencies will not resonate in that pipe?

400 Hz

Two in-phase loudspeakers that emit sound with the same frequency are placed along a wall and are separated by a distance of 5.00 m. A person is standing 12.0 m away from the wall, equidistant from the loudspeakers. When the person moves 1.00 m parallel to the wall, she experiences destructive interference for the first time. What is the frequency of the sound? The speed of sound in air is 343 m/s.

422 Hz

Water flowing through a cylindrical pipe suddenly comes to a section of pipe where the diameter decreases to 86% of its previous value. If the speed of the water in the larger section of the pipe was 32 m/s, what is its speed in this smaller section if the water behaves like an ideal incompressible fluid?

43 m/s

Consider a pipe of length L that is open at one end and closed at the other end. What are the wavelengths of the three lowest-pitch tones produced by this pipe?

4L, 4L/3, 4L/5

When a box rests on a round sheet of wood on the ground, it exerts an average pressure p on the wood. If the wood is replaced by a sheet that has half the diameter of the original piece, what is the new average pressure?

4p

An incompressible ideal fluid flows steadily through a pipe that has a change in diameter. The fluid speed at a location where the pipe diameter is 8.0 cm is 1.28 m/s. What is the fluid speed at a location where the diameter has narrowed to 4.0 cm?

5.1 m/s

A round coin has a diameter of 19.55 mm, a thickness of 1.55 mm, and a mass of 2.50 g. What is its density?

5.37 × 10^3 kg/m^3

The density of material at the center of a neutron star is approximately 1.00 × 1018 kg/m3. What is the mass of a cube of this material that is 1.76 microns on each side. (One micron is equal to 1.00 × 10-6 m.)

5.45 kg

A barge with vertical sides is 10 m wide and 60 m long and is floating in fresh water of density 1000 kg/m3. How much deeper into the water does the barge sink when 3.0 × 105 kg of coal are loaded on the barge?

50 cm

A pump uses a piston of 15 cm diameter that moves at 2.0 cm/s as it pushes a fluid through a pipe. What is the speed of the fluid when it enters a portion of the pipe that is 3.0 mm in diameter? Treat the fluid as ideal and incompressible.

50 m/s

For a certain patient, the build-up of fatty tissue on the wall of an artery has decreased the arterial radius by 10%. By how much would the pressure provided by the heart have to be increased to maintain a constant volume of blood flow? Model the blood as an ideal incompressible fluid

52%

A 13,000-N vehicle is to be lifted by a 25-cm diameter hydraulic piston. What force needs to be applied to a 5.0 cm diameter piston to accomplish this? Assume the pistons each have negligible weight.

520 N

A piano wire of linear mass density 0.0050 kg/m is under a tension of 1350 N. What is the wave speed in this wire?

520 m/s

A certain factory whistle can be heard up to a distance of 9.8 km. Assuming that the acoustic output of the whistle is uniform in all directions, at what distance from the factory is the intensity level of the whistle sound equal to 25 dB? The threshold of human hearing is 1.0 × 10-12 W/m2

550 m

A crying baby emits sound with an intensity of 8.0 × 10-8 W/m2. Calculate a reasonable estimate for the intensity level from a set of quintuplets (five babies), all crying simultaneously at the same place? The lowest detectable intensity is 1.0 × 10-12 W/m2.

56 dB

Crests of an ocean wave pass a pier every 10.0 s. If the waves are moving at 5.6 m/s, what is the wavelength of the ocean waves?

56 m

What is the frequency of a pressure wave of wavelength 2.5 m that is traveling at 1400 m/s?

560 Hz

A string that is 0.26 m long is vibrating in its n = 6 harmonic. The sound from this string excites a pipe that is 0.88 m long and open at both ends into its second overtone resonance. What is the common resonant frequency of the string and the pipe? The speed of sound in air is 345 m/s.

590 Hz

A hollow steel ball of diameter 3.0 m just barely floats in water. What is the wall thickness of the ball? (ȡFe = 7.87 g/cm3 , ȡwater = 1.00 g/cm3 )

6.6 cm

One of the harmonics of a column of air in a tube that is open at one end and closed at the other has a frequency of 448 Hz, and the next higher harmonic has a frequency of 576 Hz. What is the fundamental frequency of the air column in this tube?

64 Hz

What is the frequency does a stationary observer hear when a train approaches her with a speed of 30 m/s. The frequency of the train horn is 0.600 kHz and the speed of sound is 340 m/s.

658 Hz

The intensity level is 65 dB at a distance 5.00 m from a barking dog. What would be a reasonable estimate for the intensity level if two identical dogs very close to each other were barking? You can ignore any interference effects.

68 dB

A 1.00-m3 object floats in water with 20.0% of its volume above the waterline. What does the object weigh out of the water? The density of water is 1000 kg/m3

7,840 N

A barge is 10 m wide and 60 m long and has vertical sides. The bottom of the boat is 1.2 m below the water surface. What is the weight of the barge and its cargo, if it is floating in fresh water of density 1000 kg/m3?

7.1 MN

A 1938 nickel has a diameter of 21.21 mm, a thickness of 1.95 mm, and weighs 0.04905 N. What is its density?

7.26 × 10^3 kg/m3

The speed of sound in steel is 5000 m/s. What is the wavelength of a sound wave of frequency 660 Hz in steel?

7.58 m

A 90-gram wire that is 1.0 m long is under tension. When a transverse wave of frequency 890 Hz travels down the wire, its wavelength is 0.10 m and its amplitude is 6.5 mm. What is the tension in the wire?

710 N

If a string fixed at both ends resonates in its fundamental mode with a frequency of 150 Hz, at which of the following frequencies will it not resonate? (There could be more than one correct choice.)

75 Hz, 500 Hz

A solid object floats in water with three-fourths of its volume beneath the surface. What is the object's density? The density of water is 1000 kg/m3 .

750 kg/m3

A circular window 30 cm in diameter in a submarine can withstand a net maximum force of 5.20 × 105 N without damage. What is the maximum depth in a fresh-water lake to which the submarine can go without damaging the window? The density of fresh water is 1000 kg/m3 .

750 m

The wavelengths of the sounds produced by two horns are 6.0 m and 7.0 m, respectively. What beat frequency is heard when the horns are sounded on a day when the speed of sound is 340 m/s?

8 Hz

A styrofoam sphere of radius R has a density ȡ. You now carefully compress the sphere so its radius is R/2. What is the density of the compressed sphere?

8 p

An object has a volume of 4.0 m3 and weighs 40,000 N. What will its apparent weight be in water of density 1000 kg/m3 ?

800 N

An object weighs 7.84 N when it is in air and 6.86 N when it is immersed in water of density 1000 kg/m3 . What is the density of the object?

8000 kg/m3

Two tuning forks have frequencies of 440 and 522 Hz. What is the beat frequency if both are sounding simultaneously?

82 Hz

Two strings both vibrate at exactly 819 Hz. The tension in one of them is then increased slightly. As a result, six beats per second are heard when both strings vibrate. What is the new frequency of the string that was tightened?

825 Hz

If the intensity level by 15 identical engines in a garage is 100 dB, what is the intensity level generated by each one of these engines?

88 dB

Water, which we can treat as ideal and incompressible, flows at 12 m/s in a horizontal pipe with a pressure of 3.0 × 104 Pa. If the pipe widens to twice its original radius, what is the pressure in the wider section?

9.8 × 10^4 Pa

The lowest tone to resonate in pipe of length L that is open at both ends is 200 Hz. Which one of the following frequencies will not resonate in the same pipe?

900 Hz

A policeman in a stationary car measures the speed of approaching cars by means of an ultrasonic device that emits a sound with a frequency of 39.6 kHz. A car is approaching him at a speed of 35.0 m/s. The wave is reflected by the car and interferes with the emitted sound producing beats. What is the frequency of the beats when the speed of sound in air is 343 m/s?

9000 Hz

In a section of horizontal pipe with a diameter of 3.0 cm, the pressure is 100 kPa and water is flowing with a speed of 1.5 m/s. The pipe narrows to 2.0 cm. What is the pressure in the narrower region? Treat the water as an ideal incompressible fluid.

95 kPa

When a heavy metal block is supported by a cylindrical vertical post of radius R, it exerts a force F on the post. If the diameter of the post is increased to 2R, what force does the block now exert on the post?

F

Four waves are described by the following equations, where distances are measured in meters and times in seconds. I. y = 0.12 cos(3x - 21t) II. y = 0.15 sin(6x + 42t) III. y = 0.13 cos(6x + 21t) IV. y = -0.23 sin(3x - 42t) Which of these waves have the same speed?

I and II

The intensity of the waves from a point source at a distance d from the source is I. What is the intensity at a distance 2d from the source?

I/4

What is the wavelength of the wave shown in the figure?

It cannot be determined from the given information.

A music tuner uses a 554-Hz C# tuning fork to tune the frequency of a musical instrument. If the tuner hears a beat frequency of 2 Hz, what is the frequency of the instrument?

It could be either 556 Hz or 552 Hz

Two pure tones are sounded together and a particular beat frequency is heard. What happens to the beat frequency if the frequency of one of the tones is increased?

It could either increase or decrease.

A piece of wood is floating in a bathtub. A second piece of wood sits on top of the first piece, and does not touch the water. If the top piece is taken off and placed in the water, what happens to the water level in the tub?

It does not change

A piece of iron rests on top of a piece of wood floating in a bathtub. If the iron is removed from the wood, and kept out of the water, what happens to the water level in the tub?

It goes down.

The water pressure to an apartment is increased by the water company. The water enters the apartment through an entrance valve at the front of the apartment. Where will the increase in the static water pressure be greatest when no water is flowing in the system?

It will be the same at all faucets.

If atmospheric pressure increases by an amount ǻp, which of the following statements about the pressure in a lake is true? (There could be more than one correct choice.)

The absolute (total) pressure increases by p, The gauge pressure does not change.

As a rock sinks deeper and deeper into water of constant density, what happens to the buoyant force on it if it started above the surface of the water?

The buoyant force first increases and then remains constant.

Salt water has greater density than fresh water. A boat floats in both fresh water and in salt water. Where is the buoyant force greater on the boat?

The buoyant force is the same in both cases.

When a guitar is tuned to adjust it pitch, what is it that is changed?

The frequency of the fundamental.

A closed cubical chamber resting on the floor contains oil and a piston. If you push down on the piston hard enough to increase the pressure just below the piston by an amount ǻp, which of the following statements is correct? (There could be more than one correct choice.)

The increase in the force on the top of the chamber will be the same as the increase in the force on the bottom of the chamber., The pressure everywhere in the oil will increase by ǻp.

An pipe of length L that is open at both ends is resonating at its fundamental frequency. Which statement about the sound is correct?

The wavelength is 2L and there is a displacement node at the pipe's midpoint.

A pipe of length L that is closed at one end and open at the other end is resonating at its fundamental frequency. Which statement about the sound is correct?

The wavelength is 4L and there is a displacement antinode at the pipe's open end.

Why does the intensity of waves from a small source decrease with the square of the distance from the source?

The waves spread out as they travel.

Consider the standing wave on a guitar string and the sound wave generated by the string as a result of this vibration. What do these two waves have in common? (There may be more than one correct choice.)

They have the same period, They have the same frequency.

Substance A has a density of 3 g/cm3 and substance B has a density of 4 g/cm3 . In order to obtain equal masses of these two substances, what must be the ratio of the volume of A to the volume of B?

VA/VB = 4/3

In a resonating pipe that is open at both ends, there

are displacement antinodes at each end.

Water flows through a pipe. The diameter of the pipe at point B is larger than at point A. Where is the water pressure greatest?

at point B

A person stands between two speakers driven by the same source. Each speaker produces a tone with a frequency of 200 Hz on a day when the speed of sound is 330 m/s. The person is 1.65 m from one speaker and 4.95 m from the other. What type of interference does the person perceive?

constructive

The intensity of the waves from a point source at a distance d from the source is I. At what distance from the sources is the intensity equal to 2I?

d/√2

A boat loaded with rocks is floating in a swimming pool. If the rocks are thrown into the pool, the water level in the pool, after the rocks have settled to the bottom

falls.

A steel ball sinks in water but floats in a pool of mercury, which is much denser than water. Where is the buoyant force on the ball greater?

floating on the mercury

As you are moving very quickly toward a speaker emitting a pure tone, which characteristics of the sound get larger? (There may be more than one correct choice.)

frequency, loudness

Consider a brick that is totally immersed in water, with the long edge of the brick vertical. The pressure on the brick is

greatest on the bottom of the brick.

In many cartoon shows, a character runs off a cliff, realizes his predicament, and lets out a scream. He continues to scream as he falls. If the physical situation is portrayed correctly, from the vantage point of an observer at the foot of the cliff, the pitch of the scream as he falls should be

higher than the original pitch and increasing as he falls.

An air bubble underwater has the same pressure as that of the surrounding water. As the air bubble rises toward the surface (and its temperature remains constant), the volume of the air bubble

increases

In a resonating pipe that is open at one end and closed at the other end, there

is a displacement node at the closed end and a displacement antinode at the open end.

In a resonating pipe that is open at one end and closed at the other, there

is a displacement node at the closed end and a displacement antinode at the open end.

Salt water is denser than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of water displaced in the salt water is

less

A string fixed at both ends is vibrating in one of its harmonics. If we now increase only the frequency at which the string is vibrating, which of the following characteristics do we also increase? (There could be more than one correct choice.)

none of the above

You double your distance from a sound source that is radiating equally in all directions. What happens to the intensity of the sound? It reduces to

one-fourth its original value.

An organ pipe of length L that is open at one end resonates in its third harmonic with a wavelength of 2L/3. Is the other end of the pipe closed or open?

open

A hollow sphere of negligible mass and radius R is completely filled with a liquid so that its density is ȡ. You now enlarge the sphere so its radius is 2R and completely fill it with the same liquid. What is the density of the enlarged sphere?

p

What characteristics of a sound wave are related to the "pitch" of a musical note? (There could be more than one correct choice.)

period, wavelength, frequency

A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will

remain where it is released.

A 50-cm3 block of wood is floating on water, and a 50-cm3 chunk of iron is totally submerged in the water. Which one has the greater buoyant force on it?

the iron

Suppose that a sound source is emitting waves uniformly in all directions. If you move to a point twice as far away from the source, the frequency of the sound will be

unchanged.

A string of mass m is under tension, and the speed of a wave in the string is v. What will be the speed of a wave in the string if the mass of the string is increased to 2m but with no change in the length or tension?

v/√2

A string of length L is under tension, and the speed of a wave in the string is v. What will be the speed of a wave in the string if the length is increased to 2L but with no change in the mass or tension?

v√2

When a certain string is under tension T, the speed of a wave in the string is v. What will be the speed of a wave in the string if the tension is increased to 2T without changing the mass or length of the string?

v√2