| Terms |
Definitions |
|
ρobject/ρfluid=Vsub/V
|
Weightobj/Fbouy=
|
|
mega
|
10^6
|
|
Centi?
|
10^-2
|
|
a∆t
|
(velocity) ∆v=?
|
|
teslas
|
units of B
|
|
Workoutput / Workinput
|
Efficiency(%)=
|
|
impulse
|
change in momentum, Favgdeltat
|
|
F1 + F2 +...
|
Fnet=?
|
|
multiply (Ax10^6) and (Cx10^7)
|
(AC)x10^13
|
|
Review this pulley system.
|
|
|
2yL, (y is gamma)
|
Fsurface tension=
|
|
Inelastic Collision Equations
|
Momentum is conserved:
m(1)u(1)=m(1)v(1) + m(2)v(2)
|
|
standing wave
|
Superposition of two oppositely-directed traveling waves that result in a single, nontraveling wave
|
|
Dielectric materials
|
usually insulating material
when added to a capacitor, decreases voltage so increases capacitance
|
|
Range
|
- (Horizontal velocity) x (time)
∴ range is dictated by both horizontal and vertical velocities
|
|
Friction Force
|
Antagonistic force that points parallel and opposite in direction to the (attempted) movement of an object expressed as the product of friction coefficient and the force normal, static, kinetic (Ff = µN) or angular (tanθ = µ).
|
|
displacement
|
stating the vector, i.e.-speed and direction
|
|
750W
|
1 horsepower is how many watts?
|
|
Visible light wavelength
|
390nm to 700 nm
|
|
Constant volume
|
W = 0
Δ = Q
|
|
Mass
|
- quantitative measure of an objects inertia. tells us how much that object will resist a Δmotion
|
|
Pressure of a fluid below the surface
|
Po+pgh
|
|
Cohesion
|
Type of attractive force felt by liquid molecules toward each other. Cohesion is responsible for surface tension.
|
|
Work Function
|
Minimum amount of photon energy required to emit an electron from a certain metal. This quantity, denoted by W, is used to calculate the residual kinetic energy of an electron emitted by a metal, given by KE = hf - W. hf is the energy of a photon,
|
|
________ is a fundamental concept in physics, roughly corresponding to the intuitive idea of how much matter there is in an object.
|
Mass
|
|
Joules, and is scalar
|
The unit of KE?
|
|
frequency, f
|
# cycles per unit time
f= 1/T
|
|
Is friction conservative?
|
no; work lost in heat
|
|
Polarized light
|
light whose direction of vibration has been restricted into one plan of vibration
|
|
air resistance
|
depends on surface area, shape, and velocity
|
|
Proportional
|
As long as the object is nor permanently deformed then stress and strain are?
|
|
Electrostatics
|
Study of electric charges at rest or in motion and the forces between them.
|
|
________ is defined as the rate of change of the velocity.
|
Acceleration
|
|
Total momentum conserved but total KE is not
|
Inelastic collision
|
|
Formula for the power supplied by a voltage source
|
P=IV
|
|
exponential decay
|
n = n0e-λt
n0 = number of undecayed nuclei at t=0
|
|
Magnetic Field
|
region where a megnetic influence can be detected as a force on a magnet
|
|
What are insulators?
|
■Insulators are materials in which charges can not move freely. Nonmetals are good insulators.
|
|
What kind of image does a Negative "i" create?
|
Virtual
|
|
Law of Reflection
|
Law stating that when light waves strike a medium, the angle of incidence θi is equal to the angle of reflection θr
|
|
Another way to solve falling objects
|
put KE=PE
KE=1/2 mv^2
PE=mgh
|
|
Big Five Equation
|
can only be applied when the acceleration is constant (uniform)
|
|
What is the mirror equation
|
1/o + 1/i = 1/f
|
|
Kirchoff's law
|
at any junction, sum of currents into the point equals sum of currents directed away from the point
sum of voltage sources is equal to sum of voltage drops around a closed curcuit loop
|
|
What is Young's Modulus?
|
In solid mechanics, Young's modulus (E) is a measure of the stiffness of an elastic material. It is defined as the ratio of the stress over the strain. Young's modulus is the ratio of stress, which has units of pressure, to strain, which is dimensionless; therefore Young's modulus itself has units of pressure. The SI unit of modulus of elasticity (E) is the pascal. It can be used to predict the amount a wire will extend under tension or buckle under compression.
|
|
Torque
|
• τ is a twisting force
• τ is a vector
τ = F•r•sinθ
|
|
Completely Inelastic Collision
|
Type of collision in which the two bodies stick together after colliding, resulting in a single final mass and velocity. Momentum is conserved, Kinetic Energy is not. m₁v₁ + m₂v₂ = (m₁+m₂)vf
|
|
Its speed
|
An object moving in a circular path is said to execute uniform circular motion when what is constant?
|
|
What is diffraction
|
wave moves through an opening that is the size of the wavelength or smaller
|
|
How is conductivity measured?
|
Conductivity is the ability of a solution to conduct electric current. The principle by which instruments measures conductivity is simple - two plates (cells) are placed in the sample, a potential is applied across the plates and the current is measured. Conductivity is determined from the voltage and current values according to Ohm's Law: Conductivity =1/R=I (amps)/V (volts) . The basic unit of measurement for conductivity is the Siemens (S).
|
|
What is Continuity equation?
|
One of the fundamental principles used in the analysis of uniform flow is known as the Continuity of Flow. If steady flow exists in a channel, there exists a continuity of flow, defined as: "The mean velocities at all cross sections having equal areas are then equal, and if the areas are not equal, the velocities are inversely proportional to the areas of the respective cross sections." Thus if the flow is constant in a reach of channel the product of the area and velocity will be the same for any two cross sections within that reach. Looking a the units of the product of area (square-feet) and velocity (feet per second) leads to the definition of flow rate (cubic feet per second). This is expressed in the Continuity Equation: Q = a1v1 = a2v2. Where: Q = the volumetric flow rate (also called volume flux and it's change in volume over time) and it is constant throughout the channel. A = the cross sectional area of flow and V = the mean velocity. Q is expressed as cubic feet per second or cubic meters per second. This is the flow of an IDEAL fluid. Where the channel is the narrowest, the flow speed is greatest. The short hand way is if a problem gives the diameter of a circular part of a channel, just square the diameter to get the area if it's comparing to the channel with a different circular part because π just cancels out. I just need to make sure to use AREAS when using this equation. Always remember that in ideal fluids, volumetric flow rate remains constant at all times. The flow rate is volume of fluid passing any point in a given second. With volume flow rate, the volume of fluid flowing in must equal the volume of fluid flowing out. However, when dealing with containers that spills out water, this rule does not quite work because you're dealing with gravity. The velocity of the fluid is based on the height and on gravity. So the flow rate changes. The flow rate being constant is for a channel. With ideal fluid, fluid does NOT always move from high pressure to low pressure, it depends on other factors like gravitational forces. A fluid flows in the direction that will dissipate its energy between gravity, velocity, and pressure.
|
|
What is Continuity equation?
|
Since ideal fluids are incompressible, their volume remains constant. The volume of a fluid moving through a section of pipe is given by the cross-sectional area (A) of the pipe times the distance (d) of the pipe section. If this same volume of fluid moves completely through this pipe section in a given time (t), the rate (Q) at which volume passes through the pipe is Ad/t. Since the fluid moves a distance d in time t, its velocity is v = d/t. Therefore, Q = Av. Flow can be given in terms of mass as well. For the mass flow rate (I) multiply the volume flow rate by density I = ρQ = ρAv or mv. This is momentum (mass time velocity). In an ideal fluid, flow rate is constant. Area is inversely proportional to velocity; the narrower the pipe, the greater the velocity. Pressure has no direction. The driving force behind the direction of fluid flow is the fluid's tendency to find its greatest entropy. If all other things are equal, fluid will move from high pressure to low pressure. In a horizontal pipe of constant cross-sectional area, fluid will flow from high pressure to low pressure according to: ΔP = QR, where R is the resistance to flow and Q is the flow rate.
|
|
Yes but the atoms will dipole instead of the location of free electrons
|
Does an insulator dipole?
|
|
Capacitance SI symbol and units
|
Farad (F) 1 F=1 C/V C=Colomb, V=Voltage
|
|
What does the total horizontal distance, x, traveled by a projectile equal?
|
x = (initial horizontal velocity)(time in the air)
|
|
What is beta decay?
|
Beta decay (beta decay) can be either electron emission or positron emission. In electron emission, the neutron to proton ratio is too great and a neutron is turned into a proton and an electron. The electron is then emitted. There is also positron emission when the neutron to proton ratio is too small. A proton turns into a neutron and a positron and the positron is emitted. A positron is basically a positively charged electron. With electron emission, the proton number increases by 1 because a neutron is converted to a proton, while with position emission, the proton decreases by 1 because the proton is converted to a neutron. Electron capture is one process that unstable atoms can use to become more stable. During electron capture, an electron in an atom's inner shell is drawn into the nucleus where it combines with a proton, forming a neutron and a neutrino. The neutrino is ejected from the atom's nucleus. Since an atom loses a proton during electron capture, it changes from one element to another. For example, after undergoing electron capture, an atom of carbon (with 6 protons) becomes an atom of boron (with 5 protons). So the atomic number decreases by 1, like with positron emission, but with electron emission, the atomic number increases by one. Although the numbers of protons and neutrons in an atom's nucleus change during electron capture, the total number of particles (protons + neutrons) remains the same.
|
|
What is beta decay?
|
Beta decay is the emission of an electron OR a positron. If the atomic number increases, then an electron is released. If the atomic number decreases, then the positron is released (positron emission). Beta particles are electrons or positrons.
|
|
If presented a Torque (τ) problem...
|
• MCAT τ problems are Statics!
1. upward forces = downward forces
2. rightward forces = leftward forces
3. τ clockwise = τ counter-clockwise
use the 3 equations in order. For τ you must choose a point of rotation, but want all to act at 90° to their lever arms
|
|
greater than the coefficient of static friction uk
|
Max coefficient of static friction, us
|
|
Give Sin value for the following angles: 0, 30, 45, 60, 90, 180
|
0, 1/2, !2/2=0.7, !3/2=0.87, 1, 0
|
|
What is potential energy for springs?
|
◦PE = 1/2kx^2 (spring). ■x is distance of the end of the spring from its equilibrium position. ■k is the spring constant.■Stiff springs have a larger k because they are harder to stretch (it takes more energy to stretch them). If you pull on a spring and stretch it, then you do work. That is because you are applying a force over a displacement. Since work is the transfer of energy, we must account for to what the energy was transferred. We say that the energy was transferred into the spring. The work becomes stored energy in the spring. The work becomes potential energy in the spring. A spring can be stretched or compressed. The force of a string (Hooke's Law) is F = -kx. X is the total distance that the string is shortened, it doesn't matter if force is applied to both ends of the string, the total distance that it is shortened is x. Both ends of the string would be shortened by half the total distance. Say for instance that you have an 8kg ball and a 2kg ball placed on the same spring at the same time and the spring is compressed and released. What is the maximum height of the balls? The balls will actually reach the same maximum height - which is different than if they were on separate springs. The balls leave the spring at the time, so they will have the same velocity. This velocity is what will dictate the maximum height. What we use is 1/2kx^2 = 1/2mv^2. Then you use 1/2mv^2 = mgh. The spring potential energy of the ball first gets converted into kinetic energy, then gets converted into gravitational potential energy as it regains height. If you pull on a spring and stretch it, then you do work. That is because you are applying a force over a displacement. Since work is the transfer of energy, we must account for to what the energy was transferred. We say that the energy was transferred into the spring. The work becomes stored energy in the spring. The work becomes potential energy in the spring. A spring can be stretched or compressed. The work done on the string to stretch it or to compress it becomes the potential energy in the spring. Because what happens is, the spring has a restoring force that puts it back into place. That force is a conservative force, it's not applied, it's just the energy transfered back to equilibrium. So a question wouldn't ask what the work done was on the string by the RESTORING force, it's asking about the work done to stretch the string or compress it.
|
|
What is the graph of a discharging capacitor?
|
Mathematically, a capacitor will discharge in an infinite amount of time.
|
|
Law of Conservation of Mechanical Energy
|
• conservative forces are KE and PE are conserved within a system
• states that when only conservative forces are acting, the sum of the mechanical energies remain constant:
KE₁ + PE₁ = KE₂ + PE₂ (conservative forces only, no heat)
is simplified to...
0 = ∆KE + ∆PE (conservative forces only, no heat)
|
|
Force of tension in relation to the weight
|
A common formula for tension is?
|
|
What does it mean when ΔU increases?
|
Q increases or W decreases
work is done on the system
|
|
Why can sound travel in solids as transverse and longitudinal waves?
|
In solids, there occurs the possibility of two different types of sound waves: one type, longitudinal waves, is associated with compression (the same as all sound waves in fluids and gases) and the other, transverse waves, is associated with shear stresses, which cannot occur in fluids. The speed of compression-type waves in all media is set by the medium's compressibility and density, and the speed of shear waves in solids is set by the material's stiffness, compressibility and density. A shear stress, denoted (tau), is defined as a stress which is applied parallel or tangential to a face of a material, as opposed to a normal stress which is applied perpendicularly. Longitudinal (or compression) waves are waves that have the same direction of oscillation or vibration along their direction of travel, which means that the oscillation of the medium (particle) is in the same direction or opposite direction as the motion of the wave. Longitudinal sound waves are waves of alternating pressure deviations from the equilibrium pressure, causing local regions of compression in the same direction of travel. Transverse waves (in solids) are waves of alternating shear stress at right angle to the direction of propagation.
|
|
Is "f" positive or negative in Concave mirrors?
|
Positive (rays converge on same side as source)
|
|
Newton's Third Law of Motion
|
If Object 1 exerts a force on Object 2 ('action'), then Oject 2 exerts an equal and opposite force back on Object 1 ('reaction')
|
|
What is the Conservation of energy ?
|
◦The total amount of energy before = the total amount of energy after.
◦Gravitational potential energy is converted to kinetic energy as an object falls, but the total amount of energy stays the same.
◦Kinetic energy is converted to heat and sound energy as a crate slides to a stop on a rough surface.
Kinetic energy at the highest point of a projectile is not zero - only the vertical velocity (and acceleration and force) is zero. Even though kinetic energy is = 1/2 mv^2, the v that we use to find kinetic energy is the horizontal velocity - it stays the same throughout the whole trip of a projectile.
Always try to solve a mechanics question first by using conservation of energy.
|
|
What is the Conservation of energy ?
|
A system is any defined area that we choose to consider separately from the rest of the universe. The rest of the universe is called the surroundings. Together, mass and energy define the three basic systems in physics: the open system, where
energy and mass are exchanged with the surroundings; the closed system, where energy is exchanged with the surroundings but mass is not: the isolated system, where neither energy nor mass is exchanged with the surroundings. By definition, although the form of energy in an isolated system may change, the energy of an isolated system is conserved. Thus the Law of Conservation of Energy states that, since the universe is an isolated system, the energy of the universe remains constant. Conservation of energy does NOT say that a certain type of energy (i.e.kinetic energy or potential) must be conserved, just that the SUM of all energy types must remain constant in an ISOLATED system. In a closed system, the change in the sum of all energy types must equal the energy leaving or entering the system. Energy can enter or leave a closed system only as work or heat.
|
|
Equation for if the total energy transfer is due to forces and none to heat, the work done on an object is:
|
W = ∆KE + ∆PE + ∆Ei (no heat)
∆Ei = Internal Energy
|
|
Newton's Second Law of Motion
|
Fnet = ma , where net force = sum of all forces that act on the object (mass m). Force is measured in Newtons (N) ;
1N = 1kg.m/s²
|
|
What is the second harmonic of a string?
|
The second harmonic of a guitar string is produced by adding one more node between the ends of the guitar string. And of course, if a node is added to the pattern, then an antinode must be added as well in order to maintain an alternating pattern of nodes and antinodes. In order to create a regular and repeating pattern, that node must be located midway between the ends of the guitar string. This additional node gives the second harmonic a total of three nodes and two antinodes. The standing wave pattern for the second harmonic is shown at the right. A careful investigation of the pattern reveals that there is exactly one full wave within the length of the guitar string. For this reason, the length of the string is equal to the length of the wave.
|
|
What is the formula for impulse? J = ?
|
J = (force)(time) = Ft=mv-(initial mv) =change in p
|
|
Only on each other, not on a third object
|
To be an action paired rxn the objects must be acting on?
|
