Physics Final Quiz

When a standing wave occurs on a string,

1.Answer: many points along the string move up and down, some move more than others, and some are stationary.

You have 1 k g of liquid water and 1 k g of steam. If you want to increase the temperature of both of them by 10°C, which would require more added energy?

1.Answer: the water

Which of the following wavelengths is common to a 10-cm tube open at both ends and a 15-cm tube open at one end and closed at the other? 1.60 cm 2.30 cm 3.20 cm 4.15 cm 5.5 cm 6.Two of the above 7.Three of the above 8.None of the above

20 cm

Which of the following statements are true? (i) When a pulse on a rope reflects from a rigid boundary, it is always inverted. (ii) When a pulse on rope encounters a second rope (with different characteristics from the first) that is tied to the first one, there is only sometimes a reflected pulse.

1.Answer: (i) is true, but (ii) is false

Which of these represents an example of simple harmonic motion? (i) a bouncing ball (ii) a marble rolling back and forth in a concave bowl (iii) a tree branch vibrating (iv) someone walking back and forth across a room,

1.Answer: (ii) and (iii)

Consider an amount of water freshly melted from snow in a pan and that the water has a temperature of 1°C. What will happen to the water as its temperature is increased to 3°C?

1.Answer: It will contract slightly (its volume will decrease).

A metallic key ring of 1.00 cm diameter is placed in a fire and heated up. What would you expect would happen to the inside diameter of the ring as it heats up?

1.Answer: It will expand as the metallic portion expands.

Let's say that a gas decreases in temperature, but that its volume remains constant during this process. What happens to its internal energy in this case?

1.Answer: The internal energy decreases.

If a meter stick is metallic and is used for measuring lengths at room temperature, what will be the effect of using the same meter stick for measuring lengths outside on a snowy day?

1.Answer: The lengths measured outside would be slightly greater than those measured inside.

Which of the following is true for an oscillating spring?

1.Answer: The potential energy is greatest when the spring is the most compressed and the most extended.

A ringing alarm clock is placed in a bell jar, which is then sealed, and the air is pumped out of it. Which effect will most likely occur?

1.Answer: The sound of the ringing alarm clock will get softer as the air is pumped out.

Is it possible to add energy to an isolated material and not have the material's temperature change?

1.Answer: Yes, in some cases a material's temperature will change when energy is added to the material. In other cases, the material's temperature will not change when energy is added.

For which of the following will the phenomenon of wave interference apply? (Choose the best answer.) 1.square-shaped pulses 2.sinusoidal pulses 3.triangular pulses 4.all of these

1.Answer: all of these

Which of the following could be associated with a temperature increase for a fixed amount of gas?

1.Answer: an increase in the pressure at constant volume

Raising the temperature of air will

1.Answer: increase the speed of sound in the air.

Consider a rope hung from the top of a tall ceiling to the ground. Someone sets up waves from the bottom of the rope and watches as they propagate up the rope. The wave's speed along the vertical rope will

1.Answer: increase with vertical position up the rope.

Let's say that you are spinning a fixed-frequency buzzer attached to a string in a circular path around you at a constant speed. The frequency that you hear as you spin the buzzer

1.Answer: is the same as the frequency of the buzzer.

Sound waves may be best described as being

1.Answer: longitudinal waves.

A small, hot object makes thermal contact with a more massive, equally hot object. Consequently,

1.Answer: there will be zero net flow of energy.

Suppose that a grandfather clock is calibrated correctly at sea level and is then brought up to the top of a tall mountain. What would need to be done to calibrate the clock at the top of the mountain?

1.The bob of the pendulum should be slid slightly up the rod.

You measure the temperature of two objects and one of them is warmer than the other. From this you can conclude

1.that the warmer object contains more heat than the cooler object. 2.that the warmer object contains more internal energy than the cooler object. 3.that the warmer object was heated for a longer period of time than was the cooler object. 4.Answer: none of these statements.

For which of the following would it be most advisable to utilize a system that is damped?

1.within shock absorbers

Which of the following phrases best describes heat? 1.The total energy possessed by a body. 2.The flow of temperature to or from a body. 3.The amount of energy dissipated by friction. 4.The total energy flowing between two bodies at different temperatures. 5.The useful work that could be extracted from a body.

: The total energy flowing between two bodies at different temperatures.

Consider the two systems below, labeled A and B. Which gas has the higher pressure? 1.A 2.B 3.Neither; the pressures are the same. 4.Impossible to determine

Answer: (3), (4)

Why doesn't the melting of ocean-based ice raise as much concern and the melting of land-based ice? 1.Unlike land-based ice, ocean-based ice already displaces water, so when it melts ocean levels won't change much. 2.Because ocean-based ice is in the oceans, it will affect the level of the oceans much more than land-based ice. 3.Both ocean-based ice and land-based ice raise the same level of concern.

Answer: 1. Reasoning: Unlike land-based ice, ice floating in the ocean already displaces a quantity of liquid water whose weight equals the weight of the ice. This is the same situation as will exist after the ice melts, so the melting ocean-based ice will not change ocean levels much.

An object of mass m is attached to a horizontal spring, stretched to a displacement A from equilibrium and released, undergoing harmonic oscillations on a frictionless surface with period T0. The experiment is then repeated with a mass of 4m. Choose the new period of oscillation.

Answer: 2T0 Reasoning: The period of an object-spring system is T = 2p(m/k)1/2. Thus, increasing the mass by a factor of 4 will double the period of oscillation.

Two objects made from the same material have different masses and different initial temperatures as shown. If the bodies are placed in thermal contact, the final equilibrium temperature is most nearly: 1.27°C 2.33°C 3.40°C 4.47°C 5.None of the above 6.Cannot be determined

Answer: 47°C

A block on the end of a horizontal spring is pulled from equilibrium at x = 0 to x = A and released. Through what total distance does it travel in one full cycle of its motion?

Answer: 4A Reasoning: To complete a full cycle of oscillation, the object must travel distance 2A to position x = -A and then travel an additional distance 2A returning to the original position at x = +A.

Body A has a higher temperature than body B. Which of the following statements is true? 1.Body A will feel hotter than body B. 2.Body A contains more energy than body B. 3.If placed in contact with each other, energy will flow from body A to body B. 4.If placed in contact with a third body having temperature greater than body A, body B will absorb more heat than A. 5.More than one statement is true.

Answer: If placed in contact with each other, energy will flow from body A to body B.

Suppose you're on a hot air balloon ride, carrying a buzzer that emits a sound of frequency f. If you accidentally drop the buzzer over the side while the balloon is rising at constant speed, what can you conclude about the sound you hear as the buzzer falls towards the ground?

Answer: The frequency decreases and the intensity decreases. Reasoning: The distance between you and the buzzer is increasing. Therefore, the intensity at your location is decreasing. As the buzzer falls, it moves away from you with increasing speed. This causes the detected frequency to decrease.

Two spheres are made of the same metal and have the same radius, but one is hollow and the other is solid. The spheres are taken through the same temperature increase. Which sphere expands more?

Answer: They expand by the same amount. Reasoning: A cavity in a material expands in exactly the same way as if the cavity were filled with the surrounding material. Thus, both spheres will expand by the same amount.

When an object moving in simple harmonic motion is at its maximum displacement from equilibrium, which of the following is at a maximum? 1.velocity 2.acceleration 3.kinetic energy

Answer: acceleration Reasoning: In simple harmonic motion, the force (and hence, the acceleration) is directly proportional to the displacement from equilibrium. Therefore, force and acceleration are both at a maximum when the displacement is a maximum.

Which of the following frequencies are higher harmonics of a string with fundamental frequency of 150 Hz? a) 200 H z b) 300 H z c) 400 H z d) 500 H z e) 600 Hz

Answer: b and e Reasoning: A string fastened at both ends can resonate at any integer multiple of the fundamental frequency. Of the choices listed, only 300 Hz and 600 Hz are integer multiples of the 150-Hz fundamental frequency.

A simple pendulum is suspended from the ceiling of a stationary elevator, and the period is measured. If the accelerates upward, the period 1.increases. 2.decreases. 3.remains the same.

Answer: decreases Reasoning: An accelerating elevator is equivalent to a gravitational field. Thus, if the elevator is accelerating upward, this is equivalent to an increased effective gravitational field magnitude g, and the period will decrease. Similarly, if the elevator is accelerating downward, the effective value of g is reduced and the period increases.

As an airplane flying with constant velocity moves from a cold air mass into a warm air mass, the Mach number

Answer: decreases Reasoning: The speed of sound increases in the warmer air, while the speed of the sound source (the plane) remains constant. Therefore, the ratio of the speed of the source to that of sound (that is, the Mach number) decreases.

An object of mass m is attached to a horizontal spring, stretched to a displacement A from equilibrium and released, undergoing harmonic oscillations on a frictionless surface. The experiment is then repeated with a mass of 4m. Compared to the original total mechanical energy, the subsequent total mechanical energy of the object with mass 4m is

Answer: equal Reasoning: The total energy of the oscillating system is equal to ½ kA2, where A is the amplitude of oscillation. Since the object starts from rest at displacement A in both cases, it has the same amplitude of oscillation in both cases.

A pipe open at both ends resonates at a fundamental frequency fopen. When one end is covered and the pipe is again made to resonate, the fundamental frequency is fclosed. Which of the following expressions describes how these two resonant frequencies compare?

Answer: fclosed = 1/2 fopen Reasoning: In the fundamental mode, an open pipe has a node at the center and antinodes at each end. The fundamental wavelength of the open pipe is then twice the length of the pipe and the fundamental frequency is fopen = v over 2L. When one end of the pipe is closed, the fundamental mode has a node at the closed end and an antinode at the open end. In this case, the fundamental wavelength is four times the length of the pipe and the fundamental frequency is fclose = v over 4L

Two objects with different sizes, masses, and temperatures are placed in thermal contact. Choose the best answer. Energy travels

Answer: from the object at higher temperature to the object at lower temperature Reasoning: When two objects having different temperatures are in thermal contact, energy is transferred from the higher temperature object to the lower temperature object. As a result, the temperature of the hotter object decreases and that of the cooler object increases until thermal equilibrium is reached at some intermediate temperature.

If you are asked to make a very sensitive glass thermometer, which of the following working fluids would you choose?

Answer: gasoline Reasoning: Gasoline has the highest coefficient of expansion so it undergoes the greatest change in volume per degree change in temperature.

If you quickly plunge a room-temperature mercury thermometer into very hot water, the mercury level will

Answer: go down briefly before reaching a final reading. Reasoning: The glass surrounding the mercury expands before the mercury does, causing the level of the mercury to drop slightly. The mercury rises after it begins to get warmer and approaches the temperature of the hot water, because its coefficient of expansion is greater than that for glass

The period of a simple pendulum is measured to be T on the Earth. If the same pendulum were set in motion on the Moon, would its period be 1.less than T 2.greater than T 3.equal to T

Answer: greater than T Reasoning: The value of g on the Moon is about one-sixth the value of g on Earth, so the period of the pendulum on the Moon will be greater than the period on Earth.

One container is filled with argon gas and another with helium gas. Both containers are at the same temperature. Which molecules have the higher r m s speed? 1.argon 2.helium 3.They have the same speed. 4.not enough information to say

Answer: helium Reasoning: Since the two containers are at the same temperature, the average kinetic energy per molecule is the same for the argon and helium gases. However, helium has a lower molar mass than does argon, so the rms speed of the helium atoms must be higher than that of the argon atoms.

Balboa Park in San Diego has an outdoor organ. When the air temperature increases, the fundamental frequency of one of the organ pipes (the thermal expansion of the pipe is negligible)

Answer: increases Reasoning: The change in the length of the pipe, and hence the fundamental wavelength, is negligible. As the temperature increases, the speed of sound in air increases and this causes an increase in the fundamental frequency.

Which of the following actions will increase the speed of sound in air?

Answer: increasing the air temperature Reasoning: The speed of sound in air is proportional to the square root of the temperature. Increasing the absolute temperature, T, will increase the speed of sound. Changes in frequency, amplitude, or air pressure have no effect on the speed of sound.

Suppose you have 1 k g each of iron, glass, and water, and all three samples are at 10°C. Rank them from least to greatest amount of energy transferred by heat if enough energy is transferred so that each increases in temperature by 20°C. 1.iron, glass, water 2.water, glass, iron 3.glass, iron, water 4.water, iron, glass 5.iron, water, glass

Answer: iron, glass, water Reasoning: For a given temperature increase, the energy transfer by heat is proportional to the specific heat.

You are tuning a guitar by comparing the sound of the string with that of a standard tuning fork. You notice a beat frequency of 5 Hz when both sounds are present. You tighten the guitar string and the beat frequency rises steadily to 8 Hz. To tune the string exactly to the tuning fork, you should

Answer: loosen the string Reasoning: Since the beat frequency is steadily increasing, you are increasing the difference between the frequency of the string and the frequency of the tuning fork. Thus, your action is counterproductive and you should reverse course by loosening the string.

If the amplitude of a system moving in simple harmonic motion is doubled, which of the following quantities doesn't change? 1.total energy 2.maximum speed 3.maximum acceleration 4.period

Answer: period Reasoning: The expressions for the total energy, maximum speed, and maximum acceleration are E = ½ kA2, vmax = A(k/m)1/2, and amax = A(k/m), where A is the amplitude. Thus, all are changed by a change in amplitude. The period of oscillation is T = 2p(m/k)1/2 and is unchanged by altering the amplitude.

For a simple harmonic oscillator, which of the following pairs of vector quantities can't both point in the same direction? (The position vector is the displacement from equilibrium.) 1.position and velocity 2.velocity and acceleration 3.position and acceleration

Answer: position and acceleration Reasoning: The force producing harmonic oscillation is always directed toward the equilibrium position, and hence, directed opposite to the displacement from equilibrium. The acceleration is in the direction of the force. Thus, it is also always directed opposite to the displacement from equilibrium.

A simple pendulum is suspended from the ceiling of a stationary elevator, and the period is measured. If the elevator moves with constant velocity, the period 1.increases. 2.decreases. 3.remains the same.

Answer: remains the same Reasoning: If the elevator moves with constant velocity, the period of the pendulum is the same as that in the stationary elevator.

A pendulum clock depends on the period of a pendulum to keep correct time. Suppose a pendulum clock is keeping correct time and then Dennis the Menace slides the bob of the pendulum downward on the oscillating rod. The clock then runs 1.slow. 2.fast. 3.correctly.

Answer: slow Reasoning: The clock will run slow. With a longer length, the period of the pendulum will increase. Thus, it will take longer to execute each swing, so that each second according to the clock will take longer than an actual second.

Suppose you have 1 k g each of iron, glass, and water, and all three samples are at 10°C. Rank the samples from lowest to highest temperature after 100 J of energy is added to each by heat. 1.iron, glass, water 2.water, glass, iron 3.glass, iron, water 4.water, iron, glass 5.iron, water, glass

Answer: water, glass, iron Reasoning: Because it has the highest specific heat water has the smallest change in temperature. Glass is next and iron is last.

To have your coffee be as hot as possible when you drink it later, when should you add room temperature cream? 1.As soon as the coffee is served. 2.Just before you drink it. 3.Either; it makes no difference. 4.It is impossible to determine.

As soon as the coffee is served.

Two identical springs are attached to two identical masses. Both are resting on a frictionless horizontal surface. One of the springs is displaced a distance d from its equilibrium position, while the other is displaced a distance 2d. If both masses are released at the same instant, which of the springs, A or B, returns to its unstretched length first? 1.Spring A. 2.Spring B. 3.It's a tie. 4.Not enough information.

It's a tie

If the wavelength of sound is increased by a factor of 3, what happens to its speed and frequency?

Its frequency decreases by a factor of 3, but its speed stays the same

Two sound waves can interfere: 1.only when traveling in the same direction. 2.only when the frequencies are the same. 3.only when both are sinusoidal. 4.only when the phase difference is constant. 5.None of the above.

None of the above

Temperature is a measure of... 1.... the total amount of heat possessed by something. 2.... the flow of energy to or from something. 3.... the total energy possessed by something. 4.... the total kinetic energy of the constituents of something. 5.... the amount of useful work that could be extracted from something. 6.None of the above.

None of the above.

The intensity of a sound wave is a measure of: 1.energy/area 2.force/time 3.momentum change/time 4.power/time 5.pressure difference/time 6.None of the above.

None of the above.

The energy that flows in a sound wave is: 1.kinetic energy only. 2.potential energy only. 3.both kinetic and potential energy. 4.heat energy. 5.thermal energy. 6.all of the above.

Possible: (1), (3)

Two identical thermodynamic systems, one at T1 and the other at T2, are placed in thermal contact. When they reach thermal equilibrium, what is true about the final temperature?

Tfinal = ½(T1 + T2)

The phenomenon of interference is the result of: 1.conservation of energy 2.superposition 3.the Fourier theorem 4.conservation of mass 5.all of the above

superposition

The use of the term "sound waves" in air is meant to describe:

the pressure variations in air

Three systems are constructed from identical springs and masses as shown. Which statement is true regarding the frequencies of these systems? 1.​ω1 > ω2 > ω3 2.​ω1 > ω2 < ω3 3.​ω1 < ω2 = ω3 4.​ω1 < ω2 < ω3 5.​ω1 = ω2 < ω3 6.​ω1 = ω2 = ω3 7.None of the above. 8.Cannot be determined.

ω1 = ω2 = ω3