All AP Physics 1 Resources
Example Questions
Example Question #1 : Electricity And Waves
An open pipe (open at both ends) has a fundamental frequency of 600Hz. How long is the pipe?
An open pipe can be modeled by the following equation:
Rearrange the equation to solve for then plug in given values and solve.
Example Question #1 : Sound Waves
A student at a concert notices that a balloon near the large speakers moving slightly towards, then away from the speaker during the low-frequency passages. The student explains this phenomenon by noting that the waves of sound in air are __________ waves.
electromagnetic
longitudinal
latitudinal
torsional
transverse
longitudinal
Sound is a longitudinal, or compression wave. A region of slightly more compressed air is followed by a region of slightly less compressed air (called a rarefaction). When the compressed air is behind the balloon, it pushes it forward, and when it is in front of the balloon, it pushes it back. This only works if the frequency is low, because the waves are long enough so that the balloon can react to them.
Example Question #7 : Sound Waves
Consider a 37cm long harp string with a fundamental frequency of 440Hz.
Calculate the speed of the standing wave created by plucking this string.
Use the following equation to find the velocity of the wave, using its fundamental frequency and the length:
Example Question #11 : Sound Waves
Consider a 37cm long harp string with a fundamental frequency of 440Hz.
Suppose the string is pressed down in such a way that only a 10cm length of string vibrates. What is the speed of the wave produced when the string is plucked in terms of the speed of the wave when all 37cm of the string vibrate?
The speed of a wave is a property of the medium, it is not affected by the length of the string. The frequency may change, but the speed remains constant. There is no change in the speed.
Example Question #1161 : Ap Physics 1
Consider a 37cm long harp string with a fundamental frequency of 440Hz.
If only half of the string is allowed to vibrate, what frequency will be heard?
Since the speed of the wave does not change based on the length of the string and we know it has a fundamental frequency of 440Hz, a string of half the length will vibrate at twice the frequency, 880Hz. This makes sense as it will sound higher in pitch. You can try this with a rubber band on a shoebox. Plucking it while placing your finger halfway along the band will result in a higher pitched sound.
Example Question #1162 : Ap Physics 1
Consider a 37cm long harp string with a fundamental frequency of 440Hz.
What is the wavelength of the second harmonic of the string?
The wavelength of the second harmonic of a standing wave on a string is just the length of the string. For the second harmonic, an entire cycle occurs on the length of the string. Therefore, the wavelength of the second harmonic for this string is 37cm or 0.37m. The wavelength for the first harmonic, or fundamental, is twice the length of the string, as this is when one half a cycle occurs over the length of the string.
Example Question #14 : Electricity And Waves
If the first harmonic of a string has frequency , what is the frequency of the harmonic of that string in terms of ?
Harmonics describe the relationship between wavelengths and frequency on a string. A given string will have a wave speed associated with it. Given this wave speed, the harmonics are the frequencies at which half-wavelengths occur along the length of the string. For instance, the first harmonic is the frequency at which a half-wavelength occurs over the string. The second harmonic completes one wave over the string. The string is 1.5 times the wavelength of the third harmonic and so on. Therefore, the harmonic has a frequency of .
Example Question #11 : Sound Waves
Given that 20kJ of energy are hitting a window pane over a period of 5s with dimensions 2.5m by 4m, what is the sound level in decibels?
The formula for intensity, is:
Where is power in watts and is the surface area. The surface area in our case is:
The power can be given as or in our case:
Solve for intensity.
The formula for sound level is:
, where is the intensity and is the threshold of hearing, which is
Example Question #14 : Sound Waves
At a distance of from a fan exerting of mechanical energy, estimate the sound level if the threshold of hearing is
First we need to solve for intensity , given by:
, where is power, is the distance from the source of the sound.
In our case, and , therefore
To solve for sound level , we do
, where is the intensity and is the threshold of hearing.
In this problem,
, and
Example Question #17 : Electricity And Waves
By what factor will the sound level in decibels change if the intensity is increased by a factor of ?
Sound level will change by a factor of
Sound level will change by a factor of
Sound level will change by a factor of
Sound level will change by a factor of
Sound level will change by a factor of
Recall that the formula for sound level given in decibels is given by:
, where is the intensity and is the threshold of hearing.
Sound level is proportional to intensity by:
If the intensity is increased by a factor of , sound level would increase by a factor of
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