Physics - MCAT Chemical and Physical Foundations of Biological Systems
Card 1 of 3927
Two cars approach each other at 
when one car starts to beep its horn at a frequency of 475Hz. What is the wavelength of the horn as heard by the other driver?
Two cars approach each other at
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The Doppler equation is:
.
Because the cars are approaching each other, the frquency heard will be increased. This fundamental knowledge allows you to determine the signs of the equation. The top of the fraction will be addition and the bottom will be subtraction to make a coefficient greater than 1.
Use the given values to solve:
Now that we know the frequency, we can solve for the wavelength:
The Doppler equation is:
Because the cars are approaching each other, the frquency heard will be increased. This fundamental knowledge allows you to determine the signs of the equation. The top of the fraction will be addition and the bottom will be subtraction to make a coefficient greater than 1.
Use the given values to solve:
Now that we know the frequency, we can solve for the wavelength:
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Which of the following waves carry the greatest amount of energy?
Which of the following waves carry the greatest amount of energy?
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The energy of a wave increases with increasing frequency and decreasing wavelength. Considering these different waves, radiowaves possess the longest wavelengths and gamma rays the shortest wavelength, thus gamma rays carry the greatest amount of energy.
The energy of a wave increases with increasing frequency and decreasing wavelength. Considering these different waves, radiowaves possess the longest wavelengths and gamma rays the shortest wavelength, thus gamma rays carry the greatest amount of energy.
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The first four energy levels of a hydrogen atom have the energies given above. If a hydrogen atom is initially in the n = 2 state, photons of which of the following energies could be absorbed?
The first four energy levels of a hydrogen atom have the energies given above. If a hydrogen atom is initially in the n = 2 state, photons of which of the following energies could be absorbed?
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Absorbing a photon would have the effect of pushing the atom into a higher energy state, in this case n = 3 or n = 4. Photons with an energy equal to the difference betweeen E2 and E3 or between E2 and E4, could be absorbed.
E3 – E2 = –1.51 – (–3.40) = 1.89eV
E4 – E2 = –0.85 – (–3.40) = 2.55eV
Absorbing a photon would have the effect of pushing the atom into a higher energy state, in this case n = 3 or n = 4. Photons with an energy equal to the difference betweeen E2 and E3 or between E2 and E4, could be absorbed.
E3 – E2 = –1.51 – (–3.40) = 1.89eV
E4 – E2 = –0.85 – (–3.40) = 2.55eV
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What phenomenon can occur with light, but not sound?
What phenomenon can occur with light, but not sound?
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Sound is a longitudinal wave, while light is a transverse wave. Polarization requires the direction of the wave to be perpendicular to the direction of propogation; only light can do this. Doppler effect, refraction, and interference occur in both wave types.
Sound is a longitudinal wave, while light is a transverse wave. Polarization requires the direction of the wave to be perpendicular to the direction of propogation; only light can do this. Doppler effect, refraction, and interference occur in both wave types.
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Which statement is not true for all waves?
Which statement is not true for all waves?
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The speed of sound is dependent on the temperature of the transmitting medium. The speed of light is not.
The speed of sound is dependent on the temperature of the transmitting medium. The speed of light is not.
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What is the relationship between frequency and period of a sine wave?
What is the relationship between frequency and period of a sine wave?
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The period of a wave is equal to the reciprocal of the frequency:
Respectively, frequency is the reciprocal of period. By definition, the product of two reciprocals is one.
The period of a wave is equal to the reciprocal of the frequency:
Respectively, frequency is the reciprocal of period. By definition, the product of two reciprocals is one.
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The focal point for a mirror is 56cm behind the mirror. Is the mirror concave or convex, and what is its radius of curvature?
The focal point for a mirror is 56cm behind the mirror. Is the mirror concave or convex, and what is its radius of curvature?
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Since the focal point falls behind the mirror it must be convex. The radius of curvature can be found using the focal length equation.
Since the focal point falls behind the mirror it must be convex. The radius of curvature can be found using the focal length equation.
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A monochromatic light ray passes from air (n = 1.00) into glass (n = 1.50) at an angle of 20o with respect to the normal. What is the approximate angle of refraction?
A monochromatic light ray passes from air (n = 1.00) into glass (n = 1.50) at an angle of 20o with respect to the normal. What is the approximate angle of refraction?
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To compare angles of incidence and refraction, use Snell's law.
Notice that as the light enters a more dense medium, it bends towards the normal.
To compare angles of incidence and refraction, use Snell's law.
Notice that as the light enters a more dense medium, it bends towards the normal.
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A certain chocolate candy bar contains 
. How high can a 
barbell be lifted with the energy contained in this candy bar?
A certain chocolate candy bar contains
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Our first step is to convert kilocalories to Joules.
Now that we have converted to standard units, we can use the formula for gravitational potential energy to find the height.
We know our energy limit from the candy bar, the mass of the barbell, and the gravitational acceleration.
Solve to isolate the height.
Note that we end up with kilometers because we used kilojoules in our calculation.
Our first step is to convert kilocalories to Joules.
Now that we have converted to standard units, we can use the formula for gravitational potential energy to find the height.
We know our energy limit from the candy bar, the mass of the barbell, and the gravitational acceleration.
Solve to isolate the height.
Note that we end up with kilometers because we used kilojoules in our calculation.
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A 
ball is dropped off of a roof. If the ball takes four seconds to hit the ground, what is the ball's speed right before it hits the ground?
A
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We are given the time that the ball is in the air and the acceleration. Since the ball is dropped, we can also tell that the initial velocity is zero (starts from rest). Using these given values, we can calculate the final velocity using the appropriate motion equation.
The final velocity is negative because the ball is traveling downward; however, the question asks for speed, allowing us to disregard the vector indicator. Speed cannot be negative.
We are given the time that the ball is in the air and the acceleration. Since the ball is dropped, we can also tell that the initial velocity is zero (starts from rest). Using these given values, we can calculate the final velocity using the appropriate motion equation.
The final velocity is negative because the ball is traveling downward; however, the question asks for speed, allowing us to disregard the vector indicator. Speed cannot be negative.
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Which of the following is not a vector quantity?
Which of the following is not a vector quantity?
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Kinetic energy is calculated by squaring velocity (which we know is a vector). This eliminates its vector properties making kinetic energy a scalar value. All other answer choices are vector quantities.
Kinetic energy is calculated by squaring velocity (which we know is a vector). This eliminates its vector properties making kinetic energy a scalar value. All other answer choices are vector quantities.
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A ball of mass 3kg is thrown into the air at an angle of 45o above the horizontal, with initial velocity of 15m/s. Instantaneously at the highest point in its motion, the ball comes to rest. Approximately what is the magnitude of acceleration at this point? Assume that air resistance is negligible.
A ball of mass 3kg is thrown into the air at an angle of 45o above the horizontal, with initial velocity of 15m/s. Instantaneously at the highest point in its motion, the ball comes to rest. Approximately what is the magnitude of acceleration at this point? Assume that air resistance is negligible.
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After being thrown, the ball is only acted on by the force of gravity. Since this force is constant throughout the motion, acceleration must also remain constant, and be equal to the gravitational acceleration of 9.8 m/s2 (approximately 10 m/s2)
After being thrown, the ball is only acted on by the force of gravity. Since this force is constant throughout the motion, acceleration must also remain constant, and be equal to the gravitational acceleration of 9.8 m/s2 (approximately 10 m/s2)
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A man walks two kilometers north and then two kilometers west. What is his displacement?
- 4 kilometers
- 4 kilometers northwest
- 2.8 kilometers northwest
- 8 kilometers northwest
- none of these
A man walks two kilometers north and then two kilometers west. What is his displacement?
- 4 kilometers
- 4 kilometers northwest
- 2.8 kilometers northwest
- 8 kilometers northwest
- none of these
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Choice 3 is correct. Recall that physics problems tell you where to begin and end. The only thing that matters in figuring displacement is the beginning point and end point. The man effectively walked along the hypotenuse of a right triangle whose sides measured 2 km each. Since a2 + b2 = c2, then 4 + 4 = c2, and the correct response is the square root of 8 with the direction of the displacement added for clarity.
Choice 3 is correct. Recall that physics problems tell you where to begin and end. The only thing that matters in figuring displacement is the beginning point and end point. The man effectively walked along the hypotenuse of a right triangle whose sides measured 2 km each. Since a2 + b2 = c2, then 4 + 4 = c2, and the correct response is the square root of 8 with the direction of the displacement added for clarity.
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Five moles of nitrogen gas are present in a 10L container at 30oC. What is the pressure of the container?
Five moles of nitrogen gas are present in a 10L container at 30oC. What is the pressure of the container?
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Using the ideal gas law equation we can find that P= nRT/V. We then plug in the given values.
Solving for P gives us 12.4atm.
Note: 30oC must be converted into Kelvin by adding 273K
Using the ideal gas law equation we can find that P= nRT/V. We then plug in the given values.
Solving for P gives us 12.4atm.
Note: 30oC must be converted into Kelvin by adding 273K
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Solid A has a volume of 
and a density of 
. Solid B is cube with sides of 
and has a density of 
.
What is the difference in mass between the two solids?
Solid A has a volume of
What is the difference in mass between the two solids?
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The formula for density is:
In the question, we are given the densities of both solids and a means to find their volumes. Using these values, we will be able to determine the mass of each solid.
Now that we know both masses, we can find the difference.
The formula for density is:
In the question, we are given the densities of both solids and a means to find their volumes. Using these values, we will be able to determine the mass of each solid.
Now that we know both masses, we can find the difference.
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The law of Laplace states what relationship between that the tension in the wall of a bubble and the radius of the bubble?
The law of Laplace states what relationship between that the tension in the wall of a bubble and the radius of the bubble?
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The law of Laplace states that wall tension in a bubble, balloon, pulmonary alveolus, or blood vessel is directly proportional to the radius and the internal pressure.
Law of Laplace: 
In other words, as the size of the bubble increases at constant pressure or as the pressure increases at constant size, the wall tension needed to keep the bubble from increasing in size is increased. In part, this explains why aneurysms on blood vessels burst.
The law of Laplace states that wall tension in a bubble, balloon, pulmonary alveolus, or blood vessel is directly proportional to the radius and the internal pressure.
Law of Laplace:
In other words, as the size of the bubble increases at constant pressure or as the pressure increases at constant size, the wall tension needed to keep the bubble from increasing in size is increased. In part, this explains why aneurysms on blood vessels burst.
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Diffusion can be defined as the net transfer of molecules down a gradient created by differing concentrations of the molecule in different locations. This is a passive, spontaneous process and relies on the random movement of molecules and Brownian motion. Diffusion is an important biological process, especially in the respiratory system where oxygen diffuses from alveoli, the basic units of lung mechanics, to red blood cells in the capillaries.
Figure 1 depicts this process, showing an alveolus separated from neighboring cells by a capillary with red blood cells. The partial pressures of oxygen and carbon dioxide are given. One equation used in determining gas exchange is Fick's law, given by:
In this equation, 
is the flow rate. Area and thickness refer to the permeable membrane through which the gas passes_—_in this case, the wall of the alveolus. 
and 
refer to the partial pressures upstream and downstream, respectively. 
, the diffusion constant of the gas, is defined as:
During inspiration, the diaphragm contracts and allows oxygen to rush into the lungs. How would a change in average airway diameter affect the speed at which oxygen moves?
Diffusion can be defined as the net transfer of molecules down a gradient created by differing concentrations of the molecule in different locations. This is a passive, spontaneous process and relies on the random movement of molecules and Brownian motion. Diffusion is an important biological process, especially in the respiratory system where oxygen diffuses from alveoli, the basic units of lung mechanics, to red blood cells in the capillaries.
Figure 1 depicts this process, showing an alveolus separated from neighboring cells by a capillary with red blood cells. The partial pressures of oxygen and carbon dioxide are given. One equation used in determining gas exchange is Fick's law, given by:
In this equation,
During inspiration, the diaphragm contracts and allows oxygen to rush into the lungs. How would a change in average airway diameter affect the speed at which oxygen moves?
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Note, two of the choices say essentially say the same relationship. Therefore, one can immediately infer that they are wrong. The question is based off of knowledge of fluid dynamics. Typically, a decrease in airway diameter will provide more resistance and thus lower the speed at which a fluid (or gas) will move. Think about blowing air through a series of straws of narrowing diameter; the narrower the straw, the harder it is to blow air; therefore, a decrease in airway diameter would cause an decrease in oxygen speed.
Note, two of the choices say essentially say the same relationship. Therefore, one can immediately infer that they are wrong. The question is based off of knowledge of fluid dynamics. Typically, a decrease in airway diameter will provide more resistance and thus lower the speed at which a fluid (or gas) will move. Think about blowing air through a series of straws of narrowing diameter; the narrower the straw, the harder it is to blow air; therefore, a decrease in airway diameter would cause an decrease in oxygen speed.
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Which of the following would tend to decrease the viscosity of a liquid flowing through a pipe?
Which of the following would tend to decrease the viscosity of a liquid flowing through a pipe?
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The factors that influence viscosity are:
1. The molecular structure of the given liquid (i.e. what liquid is flowing)
2. Temperature
3. Extreme pressure
Liquids become less viscous with increased temperature. As temperature increases, the molecules move faster relative to one another and spend less time in contact with each other. This behavior causes the intermolecular forces to decrease, so the viscosity decreases.
The factors that influence viscosity are:
1. The molecular structure of the given liquid (i.e. what liquid is flowing)
2. Temperature
3. Extreme pressure
Liquids become less viscous with increased temperature. As temperature increases, the molecules move faster relative to one another and spend less time in contact with each other. This behavior causes the intermolecular forces to decrease, so the viscosity decreases.
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Use the following information to answer questions 1-6:
The circulatory system of humans is a closed system consisting of a pump that moves blood throughout the body through arteries, capillaries, and veins. The capillaries are small and thin, allowing blood to easily perfuse the organ systems. Being a closed system, we can model the human circulatory system like an electrical circuit, making modifications for the use of a fluid rather than electrons. The heart acts as the primary force for movement of the fluid, the fluid moves through arteries and veins, and resistance to blood flow occurs depending on perfusion rates.
To model the behavior of fluids in the circulatory system, we can modify Ohm’s law of V = IR to ∆P = FR where ∆P is the change in pressure (mmHg), F is the rate of flow (ml/min), and R is resistance to flow (mm Hg/ml/min). Resistance to fluid flow in a tube is described by Poiseuille’s law: R = 8hl/πr4 where l is the length of the tube, h is the viscosity of the fluid, and r is the radius of the tube. Viscosity of blood is higher than water due to the presence of blood cells such as erythrocytes, leukocytes, and thrombocytes.
The above equations hold true for smooth, laminar flow. Deviations occur, however, when turbulent flow is present. Turbulent flow can be described as nonlinear or tumultuous, with whirling, glugging or otherwise unpredictable flow rates. Turbulence can occur when the anatomy of the tube deviates, for example during sharp bends or compressions. We can also get turbulent flow when the velocity exceeds critical velocity vc, defined below.
vc = NRh/ρD
NR is Reynold’s constant, h is the viscosity of the fluid, ρ is the density of the fluid, and D is the diameter of the tube. The density of blood is measured to be 1060 kg/m3.
Another key feature of the circulatory system is that it is set up such that the organ systems act in parallel rather than in series. This allows the body to modify how much blood is flowing to each organ system, which would not be possible under a serial construction. This setup is represented in Figure 1.
Assume that in Figure 1 R1 = 1/2 mmHg/ml/min, R2 = 2 mmHg/ml/min, R3 = 4 mmHg/ml/min, and R4 = 4 mmHg/ml/min.
The pressure generated by the left ventricle is 100mmHg and the pressure generated from the right ventricle is 50mmHg. What is the rate of flow across R3?
Use the following information to answer questions 1-6:
The circulatory system of humans is a closed system consisting of a pump that moves blood throughout the body through arteries, capillaries, and veins. The capillaries are small and thin, allowing blood to easily perfuse the organ systems. Being a closed system, we can model the human circulatory system like an electrical circuit, making modifications for the use of a fluid rather than electrons. The heart acts as the primary force for movement of the fluid, the fluid moves through arteries and veins, and resistance to blood flow occurs depending on perfusion rates.
To model the behavior of fluids in the circulatory system, we can modify Ohm’s law of V = IR to ∆P = FR where ∆P is the change in pressure (mmHg), F is the rate of flow (ml/min), and R is resistance to flow (mm Hg/ml/min). Resistance to fluid flow in a tube is described by Poiseuille’s law: R = 8hl/πr4 where l is the length of the tube, h is the viscosity of the fluid, and r is the radius of the tube. Viscosity of blood is higher than water due to the presence of blood cells such as erythrocytes, leukocytes, and thrombocytes.
The above equations hold true for smooth, laminar flow. Deviations occur, however, when turbulent flow is present. Turbulent flow can be described as nonlinear or tumultuous, with whirling, glugging or otherwise unpredictable flow rates. Turbulence can occur when the anatomy of the tube deviates, for example during sharp bends or compressions. We can also get turbulent flow when the velocity exceeds critical velocity vc, defined below.
vc = NRh/ρD
NR is Reynold’s constant, h is the viscosity of the fluid, ρ is the density of the fluid, and D is the diameter of the tube. The density of blood is measured to be 1060 kg/m3.
Another key feature of the circulatory system is that it is set up such that the organ systems act in parallel rather than in series. This allows the body to modify how much blood is flowing to each organ system, which would not be possible under a serial construction. This setup is represented in Figure 1.
Assume that in Figure 1 R1 = 1/2 mmHg/ml/min, R2 = 2 mmHg/ml/min, R3 = 4 mmHg/ml/min, and R4 = 4 mmHg/ml/min.
The pressure generated by the left ventricle is 100mmHg and the pressure generated from the right ventricle is 50mmHg. What is the rate of flow across R3?
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For a parallel circuit, voltage remains constant. Analogously, pressure remains constant in this scenario. If we know the pressure and the resistance, we can find the current flow through the resistor by using ∆P = FR.
In this case, we will use only the left ventricle pressure, since that is the pressure pumped to the rest of the body, whereas the right ventricle only pumps to the lungs. Using ∆P = FR we can rearrange this to give us F = ∆P/R. Plugging in the numbers we can solve for F.
For a parallel circuit, voltage remains constant. Analogously, pressure remains constant in this scenario. If we know the pressure and the resistance, we can find the current flow through the resistor by using ∆P = FR.
In this case, we will use only the left ventricle pressure, since that is the pressure pumped to the rest of the body, whereas the right ventricle only pumps to the lungs. Using ∆P = FR we can rearrange this to give us F = ∆P/R. Plugging in the numbers we can solve for F.
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Two cars approach each other at when one car starts to beep its horn at a frequency of 475Hz. What is the wavelength of the horn as heard by the other driver?
Two cars approach each other at
Tap to reveal answer
The Doppler equation is:
.
Because the cars are approaching each other, the frquency heard will be increased. This fundamental knowledge allows you to determine the signs of the equation. The top of the fraction will be addition and the bottom will be subtraction to make a coefficient greater than 1.
Use the given values to solve:
Now that we know the frequency, we can solve for the wavelength:
The Doppler equation is:
Because the cars are approaching each other, the frquency heard will be increased. This fundamental knowledge allows you to determine the signs of the equation. The top of the fraction will be addition and the bottom will be subtraction to make a coefficient greater than 1.
Use the given values to solve:
Now that we know the frequency, we can solve for the wavelength:
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