MCAT Physics 8 Flashcards

Terms Definitions
momentum (p=)
Solid Expands
v2 + (-v1)
angle where light enters
f= (for open pipes)
region of minimum pressure
What is instantaneous velocity?
F1/A1 = F2/A2
Pascal's law =
________ kinematics or linear kinematics is the science in classical mechanics of describing the motion of a point particle.
Work-Energy Theorem
W total = ΔKE
higher to lower energy
yields fluorescence
Bulk Modulus
compression or expansion stress modulus
the transfer of energy by electromagnetic waves
If we examine this mathematical representation of a wave, when the x-axis is displacement
of the wave, the___________ is measured from any point in the wave to the point where the wave begins to repeat itself.
Potential energy only for conservative forces?
Force (F)
Mass (m) x Acceleration (a)
Absolute pressure
p = p0 + Ρgh
What are dielectrics?
■Dielectric = nonconducting material. Inserting a dielectric between the plates of a capacitor increases the capacitance by decreasing V across the capacitor while maintaining the same Q. V = V0/κ and C = κC0. A dielectric is an electrical insulator that may be polarized by the action of an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but cause dielectric polarization: positive charges are displaced along the field and negative charges shift in the opposite direction. This creates an internal electric field which partly compensates the external field inside the dielectric.If a material contains polar molecules, they will generally be in random orientations when no electric field is applied. An applied electric field will polarize the material by orienting the dipole moments of polar molecules. While the term "insulator" refers to a low degree of electrical conduction, the term "dielectric" is typically used to describe materials with a high polarizability. Dielectrics is described by the dielectric constant. A dielectric is the electrically insulating material between the metallic plates of a capacitor. The polarization of the dielectric by the applied electric field increases the capacitor's capacitance. For a given charge density, introducing a dielectric will weaken the electric field between the plates, because the negative charges of the dipoles of the dielectric shift in the opposite direction and oppose the electric field, making the electric field weaker. Since the field is weaker, it takes less work to move a charge, so now the voltage between the plates is less as well. In order to get the same voltage, you have to add a lot more charge. So the dielectric increased the capacitance of the plates, because more charges can be added to it. By putting the dielectric between the plates, the energy involved in the charge separation became less, because the field intensity became less. Dielectrics are like solvents - salt dissolves in water because water acts like a dielectric and enables the charges to separate because it makes the electric field between the positive Na and negative Cl weaker. A dipole moment = qd.
What are dielectrics?
A dielectric acts to resist the creation of an electric field, and thus allow the capacitor to store more charge (to have greater capacitance).
What do melting points correspond to?
Stacking interactions
Point of maximum displacement from the equilibrium position.
________ means a continuous change in the position of a body relative to a reference point.
a perpendicular to v means object's speed is?
convex mirror
spherical mirror with virtual focus, shiny surface curved away from objects
Adding resistors in parallel
decreases resistance
total current increases
negative image distance
image is behind mirror, virtual
What is compression?
Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is tension. In simple terms, compression is a pushing force. Compression yields noticeable amounts of stress and tension. Tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. As tension is the magnitude of a force, it is measured in Newtons and is always measured parallel to the string on which it applies. By inducing compression, mechanical properties such as compressive strength or modulus of elasticity, can be measured. Sound is transmitted through gases, plasma, and liquids as longitudinal waves, also called compression waves. Longitudinal sound waves are waves of alternating pressure deviations from the equilibrium pressure, causing local regions of compression and decompression, while transverse waves (in solids) are waves of alternating shear stress at right angle to the direction of propagation. Sound waves travel as compression waves in liquids, gases, as well as solids because the energy travels through the atomic structure by a series of compressions and expansion movements. Transverse waves (shear stress) cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave and that is why sound travels only in solids as both transverse waves and longitudinal waves, while sound only travels as longitudinal waves in liquids and gases. Transverse waves can occur on the surface of a liquid (where there is surface tension) but not through the liquid itself. Solids and liquids are nearly incompressible, if we are looking at their bulk modules, because bulk modules measures the amount of pressure from ALL SIDES of the solids and liquids and reduce their volume. Only gases can be compressed from ALL SIDES and be reduced in volume, because the gas molecules are much farther apart. However, solids, liquids, and gases can be compressed by longitudinal waves because these waves do not affect the volume of the matter, instead, the particle displacement is parallel to the direction of wave propagation.
What is compression?
Bulk's Modulus measures compression and expansion. This is ΔP/(ΔV/V), where ΔP is (F/A), and ΔV is the change in volume, and V is the original volume. The higher the bulk modulus, the less compressible the substance. So solids and liquids have higher bulk moduli than gases because they are incompressible, compared to gases.
Examples of nonconservative forces
• Kinetic Frictional Forces
• Pushing / Pulling applied by animals
ex: a human lifts an object from rest to a height, 'h'...
Total mechanical energy of the object has changed
• however, if the object was propelled by its KE to height 'h' its total mechanical energy would remain constant
Ferromagnetic Material
Material whose atoms have net magnetic field and, below a critical temperature, are strongly attracted to a magnet pole.
Focal Length
Distance between the focal point and the mirror or lens. For spherical mirrors, focal length is equal to one-half the radius of curvature.
If r or pivot point is perpendicular to force then the Torque equation is?
transverse wave
motion of medium ⊥ propagation of wave
From fast medium to slow medium, the incident of light goes __ from the normal.
In what is the speed of light fastest?
What are harmonics?
•The fundamental frequency is called the first harmonic (n = 1). The next-up frequency is called the second harmonic (1st overtone) (n = 2). Harmonics are not overtones, when it comes to counting. Even numbered harmonics are odd numbered overtones and vice versa. A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency. For example, if the fundamental frequency is f, the harmonics have frequencies f, 2f, 3f, 4f, . . . etc. The harmonics have the property that they are all periodic at the fundamental frequency, therefore the sum of harmonics is also periodic at that frequency. Harmonic frequencies are equally spaced by the width of the fundamental frequency and can be found by repeatedly adding that frequency. For example, if the fundamental frequency is 25 Hz, the frequencies of the harmonics are: 25 Hz, 50 Hz, 75 Hz, 100 Hz, etc. Music has harmonic frequencies of 2, so if you start with a fundamental of 2 Hz, then the second harmonic is 4Hz, the third harmonic is 6Hz, etc.
What are harmonics?
A list of the wavelengths from largest to smallest of the possible standing waves for a given situation is called a harmonic series. The harmonics is numbered from longest to shortest wavelength.
What kinds of images can Concave mirrors create?
Real & Virtual
Wave Speed
Speed of a wave, related to the frequency and wavelength. v = fλ
What is the range equation in projectile motion?
[d(x)]= vox t
Area under a force vs time graft is what?
angle of refraction
angle that the transmitted beam makes with normal to boundary
capacitors in parallel
can be added directly to increase total capacitance of combination
How do you determine the direction of a vector from Cartesian coordinates?
This formula
What is elastic limit?
•Elastic limit: The maximum stress something can handle before it breaks or become permanently deformed. Elastic limit, also referred to as yield point, is an upper limit for the stress that can be applied to a material before it permanently deforms. This limit is measured in Newtons per square meter, also known as pascals (Pa).
Real Image
An image produced at a point where the light rays actually converge or pass through. For mirrors, this would be on the side of the object, for lenses, it would be on the opposite side of the object.
Time of flight in projectile motion is dependent on which component?
the vertical (y)
Gravitational Potential Energy
stored energy an object has by virtue of its position in gravitational force field. It changes when the object's distance from the force of gravitational field changes
ΔPE = mgΔh
change in gravitational energy is not affected by the path taken by the object
Archimede's principle
loss in weight of an obj. immersed in a fluid equal the weight of fluid displaced
What is Thermal expansion coefficient?
◦Things expand when temperature rises, and contracts with temperature falls. All materials change their size when subjected to a temperature change as long as the pressure is held constant. ΔL = αLΔT. ΔL is the change in length, L is the initial length, ΔT is the change in temperature, and α is the coefficient of linear expansion for the substance. In the same fashion as linear expansion, the equations for volume and area expansions are below. ΔV = βVΔT. ΔA = γAΔT, where A and V are the initial areas and volumes. All materials change their size when subjected to a temperature change as long as the pressure is held constant. The coefficient of thermal expansion describes how the size of an object changes with a change in temperature. When things are heated, they expand, and therefore, their volume increases. If their volume increases, then the density of the material decreases. Also, increased volume lowers pressure, if pressure isn't constant.
What is Thermal expansion coefficient?
Solids typically expand when heated. As their molecules absorb energy, their vibrations require more room. Expansion is typically considered one dimension (linear expansion), two dimensions (area expansion), or three dimensions (volume expansion).
Angular Velocity
- a measure f the speed at which an object spins
ω = v / r
units = radians / second
is the single point at which, for the purposes of a simple mechanics problem, all the mass of that system can be considered to be concentrated. is the point through which a single force may be applied in any direction causing all points on the system to a
center of mass
What determines the frequency of a simple pendulum?
g and length of pendulum
What is polarization by scattering?
Polarization also occurs when light is scattered while traveling through a medium. When light strikes the atoms of a material, it will often set the electrons of those atoms into vibration. The vibrating electrons then produce their own electromagnetic wave which is radiated outward in all directions. This newly generated wave strikes neighboring atoms, forcing their electrons into vibrations at the same original frequency. These vibrating electrons produce another electromagnetic wave which is once more radiated outward in all directions. This absorption and reemission of light waves causes the light to be scattered about the medium. This process of scattering contributes to the blueness of our skies. This scattered light is partially polarized. Polarization by scattering is observed as light passes through our atmosphere. The scattered light often produces a glare in the skies. Photographers know that this partial polarization of scattered light leads to photographs characterized by a washed-out sky. The problem can easily be corrected by the use of a Polaroid filter. As the filter is rotated, the partially polarized light is blocked and the glare is reduced. The photographic secret of capturing a vivid blue sky as the backdrop of a beautiful foreground lies in the physics of polarization and Polaroid filters.
What is Poiseuille flow (viscosity)?
Poiseuille's law is only for REAL FLUIDS, not ideal fluids! Poiseuille law is a physical law that gives the pressure drop in a fluid flowing through a long cylindrical pipe. The assumptions of the equation are that the flow is laminar and there is no appreciable turbulence. Viscosity is a measure of the resistance of a fluid which is being deformed by either shear stress or tensile stress. Memorizing the equation for viscosity is not necessary. In real fluids, Poiseuille's law shows the dissipation of energy due to peripheral resistance, the resistance of flow from the channel itself (from friction). The pressure gets lower and lower along the channel because it's losing energy from friction. When the radius is decreased, the flow (volume flux) goes down by a lot. If pressure gradient (change in pressure) is a given, Poiseuille's law will tell you the flow rate (Q). If the flow rate is given, Poiseuille's law will tell you the change in pressure. The continuity equation assumes a constant volume flux, while the Poiseuille's law tells you what the volume flux is after taking into account the radius, the change in pressure, the length of the channel, and the viscosity. Once you know what the volume flux is, then you can use that number to determine what the velocity of the fluid will be given the cross-sectional area. Volume flux or volumetric flow rate is change in volume over time. Also, viscosity creates resistance toward the outer edge of flow. So the velocity of a fluid decreases as it moves from the middle of a channel to the outer edges (if it is viscous). This decrease in velocity is countered by an increase in pressure (just like increases in velocity result in decreases in pressure with Bernoulli equation), but this increase in pressure is on the outer edges. A viscous fluid drags along the sides of the pipe and is therefore slowed near the sides. However, even in real fluids, the fluid must maintain its velocity in the middle of the pipe or it will back up and the pipe will explode (as long as the pipe has the same cross-sectional area).
What is Poiseuille flow (viscosity)?
Viscosity is a measure of a fluid's temporal resistance to forces not perpendicular to its surface (rate of shear stress/rate of strain). A fluid's viscosity is its tendency to resist flow. Drag and viscosity are like friction and always act to impede flow. Increasing viscosity increases drag. Drag occurs at the fluid-object interface and is a force working against flow. As we move away from the fluid-object interface, the effect of drag lessens. In a real fluid flowing through a pipe, the greatest velocity would be at the center of the pipe, the spot furthest from the fluid-object interface. Because the sides of the pipe create the greatest drag, the longer the pipe, the greater the amount of fluid-object interface, and the greater is the resistance to flow. Also the more narrow the pipe, the greater the effect of drag.
For a longitudinal wave, a phase-shifted sine function represents
either the
change in pressure or the horizontal displacement of the medium with respect to
the time or d isplacement of the wave.
Center of mass (CM)
CM = point where all the object's mass can be considered to be concentrated = point that behaves as if the object were a single particle.
x (cm) = (m₁x₁ + m₂x₂ + ....) / (m₁ + m₂ + ...)
What is Potential difference (ΔV)?
■ΔV = VB - VA . Potential difference is used in scenarios such as the difference in potential between the two plates of a capacitor, or the positive and negative terminals of a battery. Consider the task of moving a positive test charge within a uniform electric field from location A to location B as shown in the diagram. In moving the charge against the electric field from location A to location B, work will have to be done on the charge by an external force. The work done on the charge changes its potential energy to a higher value; and the amount of work which is done is equal to the change in the potential energy. As a result of this change in potential energy, there is also a difference in electric potential between locations A and B. This difference in electric potential is represented by the symbol V and is formally referred to as the electric potential difference. By definition, the electric potential difference is the difference in electric potential (V) between the final and the initial location when work is done upon a charge to change its potential energy. The standard metric unit on electric potential difference is the volt, abbreviated V. One Volt is equivalent to one Joule per Coulomb. If there are 3 point charges, and you need to figure out the voltage or potential of 1 of them, with the others as given, what you do is find the potential of the charge to 1 of the charges, then the potential of the same charge to the other charge, and then add them together. That is the potential that the charge of interest. Force of an electric field is F = Eq.
What is Potential difference (ΔV)?
Voltage (V) is the potential for work by an electric
field in moving any charge from one point to another: V = Ed. Voltage is given in units of volts (V), and is a scalar. You should also recognize voltage in units of J/ c. Voltage of a point charge is also V = kq1/r. That's why Voltage is: V = Ed, E = kq1/(r^2), and you multiply it by distance and get voltage.
When changing mediums, does a wave's speed or frequency change?
The speed! Never the frequency [single wave in different media]
What is Newton's First Law?
1. Law of inertia; body in motion or at rest stay in motion or at rest unless a net force acts upon it.
What is the general nature of fission?
Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts (lighter nuclei), often producing free neutrons and photons (in the form of gamma rays), as well.
•Fission = one nuclei splitting apart. Uranium undergoes fission when struck by a free neutron. The fission of uranium generates more neutrons, which goes on to split other Uranium nuclei. This is called a chain reaction.
Equal to the weight of the fluid displaced by the object
The magnitude of the bouyant force is?
Relationship between the electric field and the electric force
The force F on a charged q located at a position where the electric field E is given by F = qE
What happens when you put a negative sign on a vector?
It maintains its magnitude but changes its direction by 180 degrees.
Explain electric field due to charge distribution for dipole, 2 charges, and vector sum.
■Field lines come out of the positive end and goes into the negative end of a dipole.
■Field lines for two negative charges would like the same as those for two positive charges except that the direction of the field lines would be reversed.
■The direction and magitude of the field at any point in space can be calculated as the vector sum of all the field components there.
Explain electric field due to charge distribution for dipole, 2 charges, and vector sum.
Notice that like the work done by gravity, the work done by an electrostatic field is independent of the path. This is because both fields are conservative; they both conserve mechanical energy. As we will see when we discuss magnetism this is not true of all electric fields.
∆psystem = 0 or total pi = totalpf
Law of Conservation of Momentum is (2 objects acting on each other)
How do you do do vector subtraction?
Add a negative vector. Do the head to tail method.
Acc=0 but there can still be v
When Fnet = 0 then what is said about the acc and vel?
What is the center of mass of particles?
The center of mass is the point at which all the mass can be considered to be "concentrated" for the purpose of calculating the "first moment", i.e., mass times distance. We are finding the distance to the center of mass for all of the particles.
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