All MCAT Physical Resources
Example Questions
Example Question #181 : Mcat Physical Sciences
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 long would it take for a 30Hz beat to reach an audience member 100m away when the ambient temperature is 21ºC?
0.31s
0.29s
0.11s
0.91s
0.29s
The question asks us to determine how long it will take for a wave beat to reach an audience member at 100m away; thus, we need to calculate the velocity of the wave to determine the time.
We know from kinematics that . This can be rearranged to solve for t: .
Example Question #21 : General Principles And Properties
A wave produced on a string travels with a velocity of . If the tension on the string is increased by a factor of four, at what speed does the wave travel?
The velocity of a wave can be obtained with the formula , where is the tension in the string and is the mass per unit length of the string. Since the tension is quadrupled, the velocity will be doubled.
Let's assume that a string with tension and a mass per unit length produces a wave with velocity .
If we increase the tension by a factor of four, we will get the below expression.
We can see that , and we know that .
Example Question #61 : Waves
Through which of the following would you expect a photon to travel fastest?
Water
Glass
Vacuum
Air
Vacuum
A photon will travel fastest through a vacuum. Photons are generally massless and can be thought of as a light wave, which travels fastest in a vacuum and slowest through a metal or solid. This can be visualized using the concept of the index of refraction, which describes the speed of light through air compared to the speed through other mediums. A vacuum will be the least dense and cause the least hindrance to a photon as it travels, thus giving it the lowest index of refraction and allowing the fastest speed of light.
Example Question #66 : Waves
You are out snorkling off the coast of an exotic island when a pod of whales comes swimming by. The pod is 100m away. If they emit sounds underwater with an average frequency of 2200Hz and there are 500 complete sound waves between you and the pod, how fast is the speed of sound in the water?
If there are 500 waves over a distance of 100 meters, we can say that the wavelength is:
Now we can use the formula for the speed of waves:
Example Question #1 : Other Wave Properties
Which statement is not true for all waves?
Wavelength is the distance between corresponding points on successive cycles
They can produce interference
They can be diffracted
Their speed depends on the temperature of the transmitting medium
Their speed depends on the temperature of the transmitting medium
The speed of sound is dependent on the temperature of the transmitting medium. The speed of light is not.
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