final physics

Find the natural frequency of vibration of the salt molecule NaCl given its effective mass of 13.9 atomic mass units and a spring constant of 100 N/m.

~10^13 Hz

A vibrating source generates a harmonic wave on a string under constant tension. If the power delivered to the string is doubled, by what factor does the amplitude change?

1.41

A grandfather clock is running slow. The period of its pendulum is too long. To shorten the period and make the clock run faster, you should.

decrease the length of the pendulum.

An ideal gas in a closed container with a piston lid is taken from thermodynamic state, 1, to a new thermodynamic state, 2, by an isothermal path as shown below in the P- V plane . Let Δ U be the internal energy change during this process, Δ Q be the heat transferred into the gas, and Δ W be the work done by the gas.

delta w is positive, delta q is positive and delta u is 0

In any process, the maximum amount of heat that can be converted into mechanical energy

depends on the intake and exhaust temperatures

In the figure below, two point sources S1 and S2, which are in phase, emit identical sound waves of wavelength 2.0 m. If L1 = 39 m and L2 = 36 m, what type of interference occurs at point P?

destructive interference

In the figure, student a has a mass of 95 kg and student b has a mass of 77 kg. They sit in identical office chairs facing each other. Student a places his bare feet on the knees of student b, as shown. Student a then suddenly pushes outward with his feet, causing both chairs to move. During the push, and while the students are still touching one another

each student exerts the same amount of force on the other

The liquid level in a glass thermometer rises as the temperature increases because

the volume expansion coefficient of glass is less than that of the liquid.

An object with mass m moves through free space with constant velocity. The magnitude of the force required to maintain this motion is equal to

zero

Newton's 3rd law is also called the law of action and reaction. The "reaction" force does not cancel the "action" force because

they act on different bodies

A string is clamped at both ends and plucked so it vibrates in a standing wave between two extreme positions as shown by the dashed lines below. If the string has length L and the frequency of oscillation of this mode is f, the speed of the waves on that string is

(2/3) fL

A container with a piston-lid contains an ideal gas at temperature Ti = 27 oC (300 K) and a volume V0. The temperature is increased to Tf = 127 oC while the pressure is kept constant. What is the new volume?

(4/3) Vo

(A) Can two force vectors of unequal magnitude sum to zero net force? (B) Can three force vectors of equal magnitude sum to zero net force?

(A) no, (B) yes

For a sound wave of frequency 440 Hz, what is the wavelength (i) in air (propagation speed, v = 3.3 * 102 m/s)? (ii) in water (propagation speed, v = 1.5 * 103 m/s)?

(i) 0.75 m, (ii) 3.41 m

The intensity of sound wave A is 100 times that of sound wave B. Relative to wave B the sound level of wave A is

+20 dB.

What is the approximate period of the sound waves shown here? (The speed of sound in air is ~340 m/s.)

.0037s

A 0.5 kg mass oscillates about the equilibrium position on a vertical spring with spring constant 10 N/m. Where is its equilibrium position measured from the unstretched spring position (without the hanging mass)?

.49 m

A point source of sound waves emits a disturbance with a power of 50 W = 50 J/s into a surrounding homogeneous medium. What is the intensity of the sound at a distance of 10 m from the source?

0.04 W/m2

If you double the radiating surface area of a star while keeping its temperature constant, its power output increases by a factor of

2

The temperature in a furnace used to melt Aluminum is 660 oC. What is the average kinetic energy of the air molecules in the furnace?

1.93*10-20 J

5 moles of a monatomic gas has its pressure increased from 10 5 Pa to 2*10 5 Pa. This process occurs at a constant volume of 0.1 m 3 . Determine the change in the internal energy of the gas. Hint : PV = nRT , U = (3/2)nRT , R = 8.31 J/K

15000 J

A 1 kg block of aluminum is heated at atmospheric pressure such that its temperature increases from 22 oC to 40 oC. What is the change in the internal energy (in J) of the block of aluminum? The specific heat of aluminum is 9*102 J/(kg K). Enter an integer.

16200

Heat is added at a rate of 10.0 kJ/min to a 0.5 kg solid sample starting at t = 0 min. What is the melting temperature of the sample? Note the units of the answers!

283K

Pure sound notes from two sources make the molecules of air at a location vibrate simple harmonically in accordance with the equations y1 = 0.008 sin (604 π t) and y2= 0.007 sin (610 π t), respectively. The number of beats heard by a person at the location will be

3

Your friends decide to play a prank on you and lock you in a room with two speakers making an incessant hum at 680 Hz. Which of the following locations would deafen the hum the most? (Take the speed of sound to be 340 m/s.)

3.00 m away from speaker A; 3.75 m away from speaker B

A standing wave is established on a 1.2 m long string fixed at both ends. The string vibrates in four segments when driven at 120 Hz. What is the fundamental frequency?

30 Hz

The temperature on a nice summer day is 84 oF. What is the temperature on the absolute (Kelvin) temperature scale?

302K

Suppose you have a tube 0.25 m long with a speaker at one end and with the other end open. If you gradually increase the frequency of the speaker from zero at about what approximate frequency will you hear the first resonance?

350 Hz

Data: cice = 0.50 cal/(g oC) , cwater = 1.00 cal/(g oC), csteam = 0.48 cal/(g oC), L(ice-water) = 80 cal/g , L(water-steam) = 540 cal/g How much heat is given off if 0.5 kg of steam at 373 K is converted into ice at 273 K?

360kcal

An ideal reversible engine takes in 5 kJ of energy via heat transferred in from a 500 K burner and exhausts heat at 300 K during each closed cycle in the PV plane. The amount of heat exhausted at 300 K each cycle is

3kJ

A stationary source S generates circular outgoing waves on a lake. The wave speed is 5.0 m/s and the crest-to-crest distance is 2.0 m. A person in a motorboat heads directly toward S at 3.0 m/s. To this person, the frequency of these waves is:

4 Hx

In the cyclic process on an ideal gas shown in the adjoining PV diagram, what is the net work done by the gas during the cycle?

4 PV

A piano tuner detects 3 beats per second when she is tuning a string to a tuning fork of frequency 440 Hz. When she tightens the string, which increases the frequency of the string, the frequency of the beats initially goes down, and as she keeps increasing the frequency of the string, the frequency of the beats starts to increase. What was the original frequency of the string?

437 Hz

A box with a total surface area of 1.2 m2 and a wall thickness of 4 cm is made of an insulating material. A 10 W electric heater inside the box maintains the inside temperature at 15 oC above the outside temperature. What is the thermal conductivity of the insulating material in units of kcal/(s oC m)?

5.3 10-6

At which temperature do the molecules of an ideal gas have 3 times the kinetic energy they have at 32oF?

546 oC

Beats are produced when two tuning forks, one of frequency 240 Hz and another of frequency 246 Hz are sounded together. The frequency of the beats is

6 Hz

By how much does the entropy of 100 g of water at 100 oC change if the water is very slowly converted into steam at 100 oC? The latent heat of vaporization of water is 540 kcal/kg = 2260 kJ/kg.

606 J/K

Ethyl alcohol boils at 172 oF. What is Celsius equivalent of this temperature?

78 celcius

An alarm clock makes a sound that has intensity 60 dB at a distance of 1 m. What is the sound intensity of 100 such clocks which are all 1 m away?

80 dB

A microwave oven is rated at 1000 W. At sea level, how long will it take to bring a cup of water (250 ml) to boil from room temperature (20 °C)? Assume the specific heat capacity of the cup itself is negligible. (for water: cw = 4190 J/(kg K), 1 ml = 1 cm3 = 1 g)

84s

A 0.500 kg mass is attached to a spring of constant 150 N/m. A driving force F(t) = (12.0 N)cos(ωt) is applied to the mass, and the damping coefficient b is 6.00 Ns/m. What is the amplitude of the steady-state motion if ω is equal to half of the natural frequency ω0 of the system?

9.7 cm

A steel bridge is built in several segments, each 20 m long. The gap between segments is 2 cm at 18 o C. What is the maximum temperature that the bridge can manage before buckling? α (steel) = 13*10 -6 /( o C)

95 celcius

A gas is in a container with a piston lid and is taken from thermodynamic state, 1, to a new thermo-dynamic state, 2, by several different paths, A, B, and C, in the P-V plane. The internal energy of the gas increases during the process. The work done by the gas is largest for path

A

We observe the harmonic motion of an object. Its position as a function of time shown in the graph below is given by x = 1* cos(π t), where x is measured in meter and t is measured in seconds. What are the amplitude (A), the period (T), and frequency (f) of the motion?

A: 1 m, T: 2 s, f: 0.5 Hz

When I bake a sweet potato in the oven, I always put it on a thin sheet of aluminum foil. This is because sometimes the potato exudes a sugary juice that burns and makes a hard-to-clean-up mess if it drips on the bottom of the oven. When I'm ready to take the potato out of the hot (400o F) oven after an hour of cooking, I find I can pick up the aluminum foil with my bare hands without getting burned. Why?

Because the aluminum foil has a low specific heat and not much mass, so even at a high temperature it doesn't have a lot of thermal energy in it to burn me.

Pressure vs. volume graphs for a certain gas undergoing five different cyclic processes are shown to the right. During which cycle does the gas do the greatest positive work?

IV

In the figures (a), (b), (c), (d) and (e) below, S is a source of sound of real frequency f and L is a listener. The speeds of the source and the listener are equal (v) in all cases except in (e) where the source is at rest and the listener is moving with speed v (as in the other cases). There is no wind. From the statements below, pick out the wrong statement.

In the case shown in fig (d) the apparent frequency as heard by the listener is less than the real frequency of the source sound going left & so is listener

An object on the end of a spring is oscillating in simple harmonic motion. If the amplitude A of oscillation is doubled, how does this affect the oscillation period T and the object's maximum speed vmax?

T remains the same and vmax doubles.

A rock is thrown straight up from the surface of the Earth. Which one of the following statements describes the energy transformation of the rock as it rises? Neglect air resistance.

The KE decreases and the PE increases.

On a humid summer day, perspiration does not cool you off much. Why?

The air is almost saturated with water vapor and there is almost no net evaporation.

A gas is in a container with a piston lid and is taken from thermodynamic state, 1, to a new thermo-dynamic state, 2, by several different paths, A, B, and C, in the P-V plane. The internal energy of the gas increases during the process. The internal energy change is largest for path

The internal energy change is the same for the three paths

You fill two identical mugs with coffee, but the coffee in one mug is at a higher temperature than that in the other mug. You place the two mugs simultaneously in a microwave oven and turn it on briefly. As a result, you add 1 Joule of thermal energy to each mug. Which mug experiences the larger increase in entropy (if any)?

The mug containing the colder coffee experiences the larger increase in entropy.

Which of the statements below is wrong?

The net force acting on the pendulum bob is F = -mgsinθ. The period increases with amplitude because this force increases faster than harmonic restoring force F= -mgθ.

A 200 Hz sound wave has a measured wavelength of 1.675 m. Which of the following statements are true? You can choose more than one statement.

The speed of the 200 Hz wave is ~335 m/s The wavelength of the 400 Hz wave is ~ 80 - 85 cm.

Suppose you are spending your weekend on roller skates trying to get momentum from somewhere. Which of the following will give you momentum in the north direction?

Throwing your keys southward.

Data: cice = 0.50 cal/(g oC) , cwater = 1.00 cal/(g oC), csteam = 0.48 cal/(g oC), L(ice-water) = 80 cal/g , L(water-steam) = 540 cal/g Which requires the most energy?

Vaporize 0.5 gram of water at T = 100 oC.

Can an object's velocity change direction when its acceleration is constant?

Yes, this is possible, and a rock thrown straight up is an example.

At a given temperature

all the molecules in a gas have the same average kinetic energy.

The Doppler effect is characteristic of

all traveling waves

A star with a surface temperature of 6000 K appears yellow in color. A star with a surface temperature of 4000 K will

appear reddish on color

Sound waves

are longitudinal waves

The P-V diagram below shows six curved paths (connected by vertical paths) that can be followed by a gas. Which two of them should be part of a closed cycle if the net work done by the gas is to be at its maximum positive value?

c & e

Living cells constitute a low entropy state of matter. Living cells

can exist because they help increase the entropy of the rest of the universe

t/f: The total entropy of the universe is always increasing. So, when water freezes, the entropy of the water is increasing.

false

A car travels over a dirt road that contains a series of equally spaced bumps (a so-called "washboard" road). While traveling at a given speed the driver experiences a very jarring ride. When the driver drives at a higher speed, however, the ride gets smoother. That is because

going faster in the car forces the suspension to oscillate at a frequency higher than its natural frequency.

A heat engine extracts usable work by permitting

heat to flow from a hotter object to a colder object

A man, with his arms at his sides, is spinning on a light frictionless turntable. When he extends his arms

his angular momentum remains the same.

In a mixture of hydrogen, oxygen, and nitrogen gases at a given temperature, the molecules having the greatest average speed are those of

hydrogen

Orange growers in Florida spray their trees with water when they expect a freeze. Why does this work?

if a mixed phase of water & ice is present, the temeprature does not drop below 0 celcius

A car's speed changes from 20 mph to 60 mph. By what factor does its kinetic energy change?

increase by 9

In any process, the maximum amount of mechanical energy that can be converted into thermal energy

is 100%

You have an empty 20 oz. soda bottle and you blow air over the opening to excite a fundamental standing wave. Now, you slice off the bottom of the bottle (it's plastic) without changing its length very much. You blow over the opening and excite a fundamental standing wave in the bottle with its bottom end open. The frequency of the standing wave in the second case

is higher than that in the first case.

A string is clamped at both ends and then plucked so that it vibrates in a standing mode between two extreme positions a and c. Let upward motion correspond to positive velocities. When the string is in position b, the instantaneous velocity of points along the string

is zero, positive, or negative, depending on the position along the string.

Consider the change a gas undergoes as it transitions from point c to point a in the PV diagram. What type of process is this?

isobaric

if the absolute temperature of a gas is halved, what happens to the average (root-mean-square or RMS) speed, √<v2>, of the gas molecules?

it decreses to 1/square root of 2 the orignial average speed

A hand moves to produce a periodic wave. You are making a movie. You freeze the movie and get this snapshot. If you advance the movie one frame, the knot at point A would be

lower.

The volume of a gaseous sample is increased from V1 to V2 in three different ways. A-->B: isobaric process A-->C: isothermal process A-->D: adiabatic process Then the work done by the gas is

maximum in the isobaric process.

Two thermometers, one calibrated in oF and one in oC, are used to measure the same temperature. The numerical reading on the Fahrenheit thermometer

may be equal, higher or lower than that on the Celsius thermometer, depending on the temperature.

An ice -cube sits in a bath of water. The water, the ice and the surrounding air are all at 0 o C. Does heat enter the ice cube?

no

A hypothetical engine operates in a cycle taking in 10,000 J from a hot reservoir and 5000 J from a cold reservoir. In the cycle it performs 15,000 J of work. Such an engine

obeys the first law but violates the second law of thermodynamics.

Assume we can change the equilibrium state of a system via two different processes. Assume that the initial and the final state are the same. Which of the quantities ΔU, ΔQ, ΔW, and ΔT must be the same for the two processes?

only ΔU and ΔT

People fighting forest fires carry emergency tents that have shiny aluminum outer surfaces. If there is trouble, a fire fighter can lie under the tent to block the heat from burning trees overhead. The tent helps because

radiation caries heat downward toward the fire fighter & the aluminum tent reflects most of that radiation

In the constellation Orion, you can easily observe the difference between the reddish looking star Betelgeuse and the bluish looking star Rigel. Which of the two has the hotter surface temperature?

rigel

When you sit facing a campfire outdoors, your face feels quite warm because

the campfire is radiatingheat towards your skin

A bullet is fired horizontally from a rifle on the Moon (no air, g = 1.6 m/s2) with initial speed v0. Assuming a level and endless ground, which statement is false?

the flight time increases as v0 increases.

The longer the wavelength of a sound wave

the lower is its pitch

A chair has a wooden seat but metal legs. The chair legs feel colder to the touch than does the seat. Why?

the metal has a higher thermal conductivity than the wood

The maintenance of the life cycle depends on

the presence of a source and a sink of energy.

The speed of sound waves having a frequency of 256 Hz compared to the speed of a sound wave having a frequency of 512 Hz is

the same

Suppose you have an aquarium. You have a solid plastic decoration and a rock of about the same volume but the rock has twice the mass. Both are totally submerged in the water. The buoyant force on the plastic object is about

the same as that on the rock.

A sinusoidal force with a given amplitude is applied to an oscillator. To maintain the largest amplitude oscillation, the frequency of the applied force should be

the same as the natural frequency of the oscillator.

You are watching a semi truck bounce up and down on a spring. (Yep it's a toy.) At the topmost point in the truck's path,

the truck's velocity is zero but its acceleration is downward.

A sine wave and a square wave cannot have the same

tone quality

true/false: It is possible to change the temperature of a system when the system is insulated from its surroundings, so that no heat can flow into and out of the system.

true

Sound does not pass through

vacuum

While a guitar string is vibrating, you gently touch the midpoint of the string to ensure that the string does not vibrate at that point. The lowest-frequency standing wave that could be present on the string

vibrates at twice the fundamental frequency.

Your dryer is broken, so you have to hang your wet clothes from the washing machine outside to dry. Under which conditions would your clothes dry fastest?

when it is 75 degrees fereinheit with 50% relative humidity

Water is flowing smoothly through the pipe shown in the diagram.

when it is in the middle (b)

In a popular classroom demonstration, a cotton ball is placed in the bottom of a strong test tube. A plunger fits inside the tube and it makes an air-tight seal. It is then pushed down very rapidly, and the cotton flashes and burns. This happens because

when the air gets compressed its temperature increases.