MCAT Physics Review Flashcards

Terms Definitions
Density (p=)
Average Velocity
Projectile acceleration: ax=
average velocity
(v + v)/2
Intensity of sound (I=)
point of zero displacement
What is instantaneous acceleration?
- magnitude only
- Ex:
(E) for tensile stress;
Young's modulus
Typically macroscopic sized objects collide in what way?
convex mirror
diverging mirror
negative focal length
peak height
Sin(theta)initial velocity = sqrt (2gh)
Electric Potential Energy (U=)
qΔV, qEd, (kq1Q)/r
Quantity measured when a constant force acts on a body to move it a distance d. Calculated as W = Fdcosθ, cosθ indicates the component force parallel to motion direction.
Total mechanical energy E=
Inertia is an object's natural resistance to change in its state of motion. It is measured by mass in kg
Newton's Law of Inertia: Fnet = 0 => v = constant
attractive force a molecule feels toward molecules of another substance
What is the relationship between acceleration and displacement?
Coulumb's constant in empty space/air = 9x10⁹ (N∙ m²)/C²
k₀ is?
Power transmitted per unit area, given by P = IA. I = Intensity, A = Area, P = Power.
Electromagnetic Spectrum
Full range of frequencies and wavelengths for electromagnetic waves broken down into the following region, in order of descending/decreasing λ: radio, infrared, visible light, ultraviolet, X-ray, Gamma Ray.
is the force resisting motion
once the two contiguous surfaces are sliding relative to each other.
Kinetic friction
If acceleration ((a) points in same direction of initial velocity (v) then the object's speed is?
an optical device (surface) that forms image by reflecting light
When does sinθ and cosθ = √2/2?
What is diffraction?
◦Diffraction is the spreading (diffusion) of waves around edges of apertures and obstacles. You can hear sounds from the other side of a building because sound spreads. Shining light through a hole will not produce a dot of light, instead, it is a diffuse circle. Diffraction is the basis for the single and double slit interference experiments with light. When you think of diffraction, think "diffuse". Diffraction refers to various phenomena which occur when a wave encounters an obstacle. It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. The smaller the opening and larger the wavelength (like with red light), the greater the bending of the wave. The smaller the hole, the greater the spreading of the light.
• Transfer of energy by natural flow from warm to cold.
the transfer of heat by the physical motion of the heated material (fluids only)
Scalar quantity used as a measure of an object's inertia.
Pascal's Principle
Principle stating that when a pressure is applied to one point of an enclosed fluid, that pressure is transmitted in equal magnitude to all points within that fluid and to the walls of its container. This principle forms the basis of the hydraulic lift.
The area under a velocity vs time graph is?
longitudinal wave
motion of medium || propagation of wave
What color is the combination of all the wavelengths of visible light?
When is torque postitive? negative?
counterclockwise motion creates positive torque
clockwise motion creates negative torque
What are equipotential lines?
■Equipotential lines are places where the potential is the same.
■Equipotential lines are always perpendicular to electric field lines.
All points on an equipotential surface are at the same voltage. An equipotential surface can be drawn at any point in the field.
Volume of water that passes a perticular point per unit of time
Flow rate is?
Destructive Interference
When two overlapping waves are out of phase, they subtract and cancel each other out if they have the same amplitude and are 180˚ out of phase
wave in which the medium is displaced perpendicularly to the direction of wave propagation, such as waves on a string.
transverse wave
Conservation of energy formulas, because reactions KE only conserved for elastic collisions
TYPICALLY don't solve collisions problems with what?
Ohm's Law
A conductor obeys Ohm'S Law if its resistance is dependent of applied voltage, i.e if R remains constant even if V is changed
Total internal reflection
all incident light is reflected back into original material
What is a unit?
A well-defined quantity with which other quantities are compared in a measurement.
What is Surface tension?
◦Surface tension gives the surface of a liquid the ability to support things that are very light.
◦For example, insects can walk on water due to surface tension.
◦Surface tension is due the attraction between the molecules of the solvent.
Surface tension is the intensity of the intermolecular forces per unit length. Much like a spring, when the molecules at the surface of the water are pushed downward by the weight of the needle, the intermolecular bonds of the water are stretched, and push upward with a force. Surface tension is also responsible for the formation of water droplets. Intermolecular forces pull inward tending to minimize the surface area by creating a more spherical shape. A sphere has the least surface area per volume of any shape. Since surface tension is a function of the intermolecular forces, it is dependent upon the temperature of the fluid (the higher the temperature, the weaker the intermolecular forces because the molecules have more energy and move about more and can escape, and so the weaker the surface tension) and upon the fluid with which it is interfacing.
What is Surface tension?
Related to surface tension is the phenomenon of capillary action, where a fluid may be pulled up a thin tube. For capillary action, recognize that there are 2 types of forces acting: the intermolecular forces responsible for surface tension (cohesive forces); and the forces between the molecules of the tube and the fluid molecules (adhesive forces). If the cohesive forces are stronger, a convex meniscus is formed and the fluid is pulled downward by the vertical component of the surface tension. If the adhesive forces are stronger, a concave meniscus is formed and the fluid is pulled upward by the vertical component of the surface tension.
In Mirrors, how does f relate to r?
f = 1/2*r
The area beneath the curve has no
meaning for a
displacement versus time graph.
Friction (f)
f = the component of the contact force exerted by a surface that is parallel to the surface
Static friction (fs)
force overcome to set an object in motion
0 ≤fs≤ μsN
What is resonance?
Resonance is the tendency of a system (usually a linear system) to oscillate at larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies (or resonance frequencies). At these frequencies, even small periodic driving forces can produce large amplitude oscillations. The diagram shows examples of standing waves and the resonance frequencies that produce them. Frequencies can be obtained by f = v/λ
Newtons 1st law
- law of inertia
- an object in a state of rest or motion will remain in that state unless acted on by an net force
parallel plate capacitor capacitance
C = ∈₀(A/d) where ∈₀ is the permitticity of free space: 8.85 x 10⁻¹² F/m
Normal Force (N)
N = the component of the contact force exerted by a surface that is ⊥ to the surface. The magnitude of the normal force on an object is not always equal to the object's weight
How does Bernoulli's equation relate to uniform translational motion of fluids?
From Bernoulli's equation we can derive an important notion about the relationship between pressure and velocity in ideal fluid flow. As velocity increases, pressure decreases. Uniform translational kinetic energy is achieved by borrowing energy from the random translational kinetic energy, thus pressure goes down. By having a high velocity (kinetic energy), some of the energy is borrowed from the pressure (potential energy).
What are Standing waves (nodes, antinodes)?
◦Standing waves vibrate at resonance frequencies.
◦Standing waves do not propagate like other waves (that's why they're called standing waves, they are not traveling waves. They are bound in place.).
◦Node: point where there's no oscillation.
◦Antinode: point where there's maximum oscillation - it's anti the node (it's anti the max oscillation). Electrons are an example of standing waves, because they vibrate in place.
The spacing between nodes in a standing-wave pattern is λ/2. A half wavelength has a node at each end, so the spacing between nodes is λ/2. You can also find the λ of a closed standing wave as λ = 2L/n. But in general, there is only a half of a wavelength between 2 adjacent nodes.
What are Standing waves (nodes, antinodes)?
Standing waves (if they are not held by a string), are created by 2 sine traveling waves with equal amplitude, frequency and wavelength that are traveling in opposite directions.
Permeability of Free Space, µ₀
Term denoted by µ₀ and equal to 4∏ X 10⁻⁷. Tesla meter/ampere; used in the equation measuring the magnetic field produced by a current-carrying wire, B = µ₀I/2∏r.
Newton's second law in terms of momentum
Fnet = Δp/Δt
Jnet = Δp (impulse-momentum theorem)
Center of Gravity
A point in or on the obj. where all the weight is concentrated. If supported only @ this point the obj. will balance
What is the relationship between Wavelength, frequency and wave speed (velocity)?
◦v = fλ
◦v is velocity, f is frequency, and λ is wavelength.
◦Some times, frequency is also written as ν.
◦Wavelength is in meters, frequency is in Hertz and velocity is in meters per second. Wavelength is how many meters per cycle, while frequency is cycles per second. The period is seconds per cycle.
Wave velocity is a constant in a nondispersive medium; it is independent of frequency, wavelength, and amplitude. So, since the velocity of the wave on a string is a function of the properties of the string, it will remain constant. If the length of the string is constant, then the wavelength of the standing wave is constant. If the velocity and wavelength are constant, then frequency is constant too. Velocity of a wave is independent of the wavelength and frequency and dependent on the medium. So changing the frequency won't change the velocity of a wave, but will change its wavelength.
What is the relationship between Wavelength, frequency and wave speed (velocity)?
Velocity is dictated by the medium. Two aspects of the medium affect the velocity: 1) the medium's resistance to change in shape (elasticity) and 2) the medium's resistance to change in motion (or inertia).
Velocity for a gas increases with temperature. Velocity is constant for any given medium.
Would increased rotational inertia make you more prone to falling?
No -- it would stabilize you with its tendency to keep you at rest
How does a projectile horizontal velocity change during a flight if air resistance is ignored?
It doesn't (b/c there is no horizontal acceleration, only the vertical acceleration due to gravity)
What are mirror curvature, radius, and focal length?
■mirror curvature can be concave or convex.
■concave mirrors can focus light, so it's converging.
■convex mirrors can't focus light, so it's diverging.
■The focal length for a mirror is 1/2 of the radius of curvature. f = 1/2r
■converging mirrors have positive focal length, while diverging mirrors have negative focal length.
■It's called the focal length because rays parallel to the principle axis of the mirror will converge at the focal point (for diverging mirrors, the extrapolated rays will pass through the focal point).
The focal point for a lens is affected by the refractive indices of the lens and the medium that the lens is in. It is also affected by the radii of the curvature of both sides of the lens.
Since the index of refraction varies for different frequencies, the focal point of a lens also varies with frequency resulting in chromatic aberration.
What are mirror curvature, radius, and focal length?
The closer the index of refraction (n) for a lens or a mirror is to the surrounding medium, the less it will refract light. For instance, if you have a glass lens that you are using to magnify light in the air, it has a bigger difference in n than the glass and water. So the magnification would decrease between the glass and water from the glass and air. If a lens is immersed in a fluid with an equal index of refraction, it will not refract light at all.
How does a floating object's weight compare to the buoyant force it feels?
for a floating object w floating = B
What are the components of a vector?
The projection of a vector on a Cartesian (x,y) coordinate system.
To be the opposite of the work done by the gravitational force
The change in gravitational potential energy is defined
What is weight equal to when someone is on a horizontal plane and an inclined plane?
•When something is laying still on a horizontal surface, the normal force is equal and opposite to the weight.
•When something is laying still on an inclined plane, the normal force and friction force adds up in a vector fashion to equal the weight.
When an object is sliding down an inclined plane, acceleration is constant (g) and in the downward direction. The horizontal velocity is also increasing, because acceleration has a component in the horizontal direction - which makes sense because a = v/t. If the object was sliding up the inclined plane, then acceleration would be decelerating, and horizontal velocity would be decreasing because acceleration acts in the downward direction, not upward direction. Remember, as long as there is friction, there is a normal force to calculate. And if there are applied forces, there is a normal force for each applied force. If there is an object on an inclined plane that is just sliding with no applied force, there is still a normal force perpendicular to that plane that corresponds with the force of gravity that's pulling that object down the plane.
How to find a slope of curvilinear graph
the slope of a line tangent to the curvilinear graph at that point
What is the potential energy due to electric dipoles?
A dipole will rotate to align with an uniform electric field, but feel no net force. Since the dipole tends to rotate, it must experience a net torque. The potential energy of a dipole is the energy that is stored in the dipole when it is away from equilibrium before it moves to equilibrium. If the field is not uniform, the dipole will experience a net force. This means the force depends on how the field changes. If the dipole is allowed to rotate it will come to equilibrium (if there are losses in the system) with its dipole moment aligned with the field. This behavior implies the dipole is seeking the minimum in potential energy. To calculate the potential energy of an electric dipole with orientation θ with respect to a uniform field, we have to calculate the work required to rotate the dipole from the location of zero potential energy (equilibrium) to the orientation θ away from equilibrium. The difference in potential energy, ∆U, is the energy due to the position of the dipole when it is away from equilibrium. rotate the dipole. E = F/q. The potential energy U of an electric dipole with dipole moment p in a uniform electric field E is U = -p*EcosΘ, where Θ is the angle between the dipole and the field. Negative sign indicates the decrease in potential in the direction of the field as the angle gets smaller. When the angle approaches 90°, cos90° is 0, so the potential energy becomes more positive and becomes larger until it reaches zero. The potential energy of a dipole represents the binding energy of the dipole when it is aligned to the electric field.
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