AP Physics 2 : AP Physics 2

Study concepts, example questions & explanations for AP Physics 2

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Example Questions

Example Question #181 : Ap Physics 2

An electron falls from an excited state to its ground state, emitting a photon at . What is the frequency of the emitted light?

Possible Answers:

Correct answer:

Explanation:

The relationship between wavelength and frequency is given by the equation:

In this case, the velocity will be equal to the speed of light.

Using this value and the given wavelength, we can find the frequency of the photon. Keep in mind that the wavelength must be given in meters.

Example Question #21 : Light

Which of  the following is/are ionizing radiation?

  1. microwaves
  2. X-rays
  3. gamma rays
  4. all of the above
  5. 2 and 3, but not 1
Possible Answers:

1

3

4

2

5

Correct answer:

5

Explanation:

Choice 5 is correct.  Highly energetic frequencies such as X-rays and gamma rays can displace electrons from materials upon which they impinge.  Microwaves are a form of radio waves, which are long-wavelength, low frequency waves with little energy. 

Mnemonic:  Microwave ovens are fundamentally safe household items.

Example Question #1 : Velocity And Waves

Sound traveling at a velocity, V1, through a certain medium will travel at what velocity through a medium of twice the density?

Possible Answers:

¼ V1

½ V1

2 V1

It depends on the medium’s resistance to compression

Correct answer:

It depends on the medium’s resistance to compression

Explanation:

The speed of sound depends on both the medium’s density and resistance to compression. We do not have enough information to solve for V2 in terms of V1.

Example Question #1 : Pendulums

For a pendulum undergoing simple harmonic motion, the ratio of the weight of the pendulum and the displacement of the pendulum from the bottommost point in its path always equals __________.

Possible Answers:

the spring constant

the tension in the string

the gravitational constant

the sum of the kinetic and potential energy of the object

Correct answer:

the spring constant

Explanation:

Hooke’s law, which is applicable to simple harmonic motion, states the relationship between force (F) and displacement (d).

k is equal to the spring constant. The ratio of F (force) to x (displacement) will be equal to the magnitude of k. In our set-up, the force is equal to the weight of the pendulum, so the ratio of weight to displacement is equal to the spring constant. This is true of all pendulums, and is given by the equation .

Example Question #1 : Longitudinal And Transverse Waves

At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as  sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of , where T is the temperature in °C.

What type of waves are sound waves?

Possible Answers:

Transverse

Electromagnetic

Gravitational

Longitudinal

Correct answer:

Longitudinal

Explanation:

Sound waves are longitudinal waves, meaning that the waves propagate by compression and rarefaction of their medium. They are termed longitudinal waves because the particles in the medium through which the wave travels (air molecules in our case) oscillate parallel to the direction of motion. Alternatively, transverse waves oscillate perpendicular to the direction of motion. Common examples of transverse waves include light and, to a basic approximation, waves on the ocean.

Example Question #1 : Velocity And Waves

At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as  sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of , where T is the temperature in °C.

How does the speed of sound in the summer (30­oC) compare to the speed of sound in the winter (9oC)?

Possible Answers:

Speed of sound in summer is 0.81 times the speed of sound in winter

Speed of sound in summer is equal to the speed of sound in winter

Speed of sound in summer is 1.04 times the speed of sound in winter

Speed of sound in summer is 1.2 times the speed of sound in winter

Correct answer:

Speed of sound in summer is 1.04 times the speed of sound in winter

Explanation:

This question asks us to use information provided in the paragraph about how the speed of sound varies with temperature. We can see from the relationship provided that in warmer temperatures the speed of sound is faster. This intuitively makes sense—hotter temperatures mean that air molecules are moving around more, and thus have less resistance to compression or rarefaction by a propagating sound wave. Now that we have a qualitative understanding, we need to compute the ratio of the velocities.

Example Question #1 : Intensity And Decibels

At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as  sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of , where T is the temperature in °C.

If the sound crew wanted to quadruple the intensity of the sound, they could __________.

Possible Answers:

halve the amplitude of the sound wave

halve the frequency of the sound wave

halve the air density

double the amplitude of the sound wave

Correct answer:

double the amplitude of the sound wave

Explanation:

This question asks us to determine what would happen to the intensity of a sound wave if a variable could be changed. First, we need to remember the equation for intensity: , where A is the wave amplitude, rho is the density of the medium, f is the frequency of the wave, and v is the velocity of the wave.

This formula is important to understand qualitatively. For the MCAT, it is important to understand how the various factors impact the intensity of a wave. If we wanted to quadruple the intensity, we can see that we could double amplitude or double frequency. Seeing that we want the sound pitch to remain the same, we would want to double the amplitude and not the frequency. The relationship between intensity, frequency, and amplitude is important to understand.

Example Question #12 : Sound

At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as  sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of , where T is the temperature in °C.

If the sound crew wanted to halve the intensity of the sound, they could __________.

Possible Answers:

double the frequency of the sound wave

halve the size of the room

double the amplitude of the sound wave

double the size of the room

Correct answer:

double the size of the room

Explanation:

This question asks us to determine what would happen to the intensity of a sound wave if a variable could be changed. First, we need to remember the equation for intensity, , where P is the power of the wave, A is the area,  is the wave amplitude, rho is the density of the medium, f is the frequency of the wave, and v is the velocity of the wave.

This formula is important to understand qualitatively. For the MCAT, it is important to understand how the various factors impact the intensity of a wave. If we wanted to halve the intensity, we can see that we could halve the power of the wave or double the area the wave is hitting; thus, we could double the size of the room, allowing the sound wave to have more room to spread out and increasing the area the wave interacts with.

Example Question #41 : Waves

At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as  sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of , where T is the temperature in °C.

What is the wavelength of a 150Hz beat at 20ºC?

Possible Answers:

1.7m

3.1m

2.3m

4.2m

Correct answer:

2.3m

Explanation:

This question is asking us to determine the wavelength of a sound wave at a specific temperature. From the equation presented to us in the paragraph above, we can calculate the wave velocity.

Now, we can use this velocity to calculate the wavelength.

Example Question #1 : Longitudinal And Transverse Waves

Which of these is an example of a longitudinal wave?

Possible Answers:

A wave produced by a rope oscillating in a plane

X-rays

Visible light

Microwaves

A sound wave

Correct answer:

A sound wave

Explanation:

Longitudinal waves transmit energy by compressing and rarefacting the medium in the same direction as they are traveling. Sounds waves are longitudinal waves and travel by compressing the air through which they travel, causing vibration.

Light, X-rays, and microwaves are all examples of electromagnetic waves; even if you cannot recall if they are longitudinal or transverse, they are all members of the same phenomenon and will have the same type of wave transmission. Transverse waves are generated by oscillation within a plane perpendicular to the direction of motion. Oscillating a rope is a transverse wave, as it is not compressing in the direction of motion.

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