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Force/area
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Stress=
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ac=v2/r
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Pico?
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10^-12
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rsin(theta)
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Lever arm=
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modulus x strain
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Stress=
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−WbyFgrav
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∆PEgrav also equals?
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Tangential Velocity
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v = rω
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d=½(Vo+V)t
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Big 5 missing a?
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insulators
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retard flow of electricity
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What are concave mirrors?
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Pgauge = (ρfluid)∙g∙D
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Hydrostatic gauge pressure=
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v₀cos (theta)₀
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Projectile motion acc: v₀x=
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rms voltage
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Vrms = Vmax /√2
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Resistivity
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intrinsic resistance to current flow
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Normal force is always equal to...
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mgcosθ
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Velocity
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Vector quantity describing an object's displacement over the elapsed time. v = Δx/Δt
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gm= G((Mm/r²)
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Weight is gravitational force so
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The ability to do work
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Energy is?
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transverse waves
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particles oscillate perpendicular to direction of wave motion
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conduction
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direct transfer of energy from molecule to molecule via collisions
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Projectile motion
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- Separate into two different motions
1. Vertical motion: acceleration is constant (10 m/s²)
2. Horizontal motion: acceleration is a constant zero
vertical: V = V (sinθ)
horizontal V = V (cosθ)
* vertical V dictates the time of flight
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Electron Volt
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Voltage created by a potential difference between the two terminals of a cell when no current is flowing.
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Heat of Vaporization
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Heat of transformation corresponding to a phase change from liquid to gas or gas to liquid.
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Positron
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An anti-electron, denoted ß+ or e+, emitted in a nuclear reaction.
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________ is the branch of classical mechanics that is concerned with the effects of forces on the motion of objects.
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Dynamics
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action-reaction pair
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requires *2 objects, *2 forces
cannot have an action-reaction pair for 2 forces acting on 1 object
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Pressure
P
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Force / Area
F
A
height * density * acceleration due to gravity
hdg
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capacitor
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two plate system connected to a voltage device that stores charge
C = Q/V
C = ε0A/d
(capacitance depends on geometry of plate)
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What are the derived equations for constant acceleration?
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Picture.
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dialectric constant
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defined by substance in a capacitor, greater than or equal to 1, and determines charge necessary to create an electric field
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Yes
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Is the potential the same at every point that's a distance r from q?
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Direct Current
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Current that flows through a conductor in one direction only.
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increases air resistance because it allows for more collisions
with air molecules.
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Large surface area
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diverging lens
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lens with virtual focus, thinner in middle than near edges
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Critical angle
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refracted angle is 90°
if angle is greater than the critical angle, total internal reflection occurs
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What is force?
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•There are 4 universal four-ces... get it? Universal forces are also called fundamental forces. The four forces are: The strong force: also called the nuclear force. It is the strongest of all four forces, but it only acts at subatomic distances. It binds nucleons together (binds protons and neutrons together to form the nucleus of an atom). Electromagnetic force: about one order of magnitude weaker than the strong force, but it can act at observable distances. Binds atoms together. Allows magnets to stick to your refrigerators. It is responsible for the fact that you are not falling through your chair right now (MCAT people love to throw you quirky examples like this one). Weak force: roughly 10 orders of magnitude weaker than the strong force. Responsible for radioactive decay. Gravity: roughly 50 orders of magnitude weaker than the strong force. Responsible for weight (not mass!). Also, responsible for planet orbits.
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deltaP
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=QR, where R = resistance in a real liquid
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What is the equation for capacitance with a dielectric in place?
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C = K(e0A/d)
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Longitudinal Wave
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Type of wave, such as sound, whose oscillation is along the direction of its motion.
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mg cos theta
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The normal force exerted by the inclined plane=
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flow rate
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Flow rate, f = Av, where A= cross-sectional area of flow tube and v = avg flow speed at that point
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What makes real inverted image
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converging lens and concave mirror
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Refraction
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bending of a wave on going into a second medium
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What are dielectrics?
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■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.
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What are dielectrics?
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A dielectric acts to resist the creation of an electric field, and thus allow the capacitor to store more charge (to have greater capacitance).
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Static Friction (Fs)
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• The force opposing motion when 2 contiguous surfaces are not moving relative to each other.
ex: block on an inclined plane and the block does not slide
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Volume Expansion
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Expansion in volume of a liquid as a result of increasing temperatures, calculated by ΔV = ßVΔT. V = volume, ß = coefficient of volume expansion, T = temperature.
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Collision b/n 2 objects
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Conservation of momentum is used to analyze what?
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Define Translational motion.
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motion in which the position of the object's center of mass changes as a function of time
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What is a voltmeter?
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A voltmeter measures the change in voltage between two points in an electric circuit and therefore must be connected in parallel with the portion of the circuit on which the measurement is made. In analogy with a water circuit, a voltmeter is like a meter designed to measure pressure difference. It is necessary for the voltmeter to have a very high resistance so that it does not have an appreciable affect on the current or voltage associated with the measured circuit. Suppose we connect a cell to a high resistance voltmeter. (A perfect voltmeter has infinite resistance. A digital multimeter has a very high resistance, so gives out a tiny current; it is almost perfect.
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What is the formula for charge w/capacitance?
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Q = VC {QVC channel}
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Newtons 3rd law
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For every action there is an equal and opposite reaction
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A person walks 2 miles north then turns around and walks 3 miles south. Total time elapsed-1 hour. Find the distance, displacement, avg. velocity, avg. speed
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distance=5 milesdisplacement=1 mile southavg. velocity=1mi/hr (S)avg. speed=5 mi/hr
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What are converging and diverging lenses for thin lens?
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◦You don't have to re-learn everything for lenses, because they are almost the same as mirrors: Convex lenses are the same as concave mirrors (both are converging) except for the following: Real images are on the opposite side of the lens as the object. Because light travels through the lens and can focus on a screen behind the lens. Virtual images are on the same side of the lens as the object. Because light can't focus in front of a lens and be cast on a screen. Concave lenses are the same as convex mirrors (both are diverging) except for the following: The virtual images formed by the lens is on the same side of the lens as the object. Because light can't focus in front of a lens and be cast on a screen. The image height vs. object distance curve is exactly the same as those of mirrors (convex lenses the same as concave mirrors, concave lenses the same as convex mirrors). Diverging lenses form reduced, erect, virtual images.
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What are converging and diverging lenses for thin lens?
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Here's a trick to remember a converging LENS: Remember the 3 C's: A thiCk Center Converges light. If the center of a lens is thicker than its ends, it will converge light, regardless of its shape or which direction light moves through the lens. If the center is thinner, it will diverge light.
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Elastic Potential Energy (EPE) (Ue)
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• energy due to the resistive force applied by a deformed object
Follow Hookes Law:
Ue = ¹/₂ K∆x²
∆x = displacement from the relaxed state
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Yes, because acceleration is occuring due to direction change
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Can the acceleration be changing while the speed doesn't in uniform circular motion?
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What does it mean when ΔU decreases?
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Q decreases or W increases
work done by the system
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How are the normal force and frictional force divided on an inclined plane?
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•Gravity is divided into two components on an inclined plane.
◦One component is normal (perpendicular) to the plane surface: FN = mg·cosθ. This component is used to calculate the frictional force and static force.
◦The other component is parallel to the plane surface: F|| = mg·sinθ. This is used to calculate the force down the plane.
•To prevent the object from crashing through the surface of the inclined plane, the surface provides a normal force that is equal and opposite to the normal component of gravity.
•Friction acts parallel to the plane surface and opposite to the direction of motion.
•In a non-moving object on an inclined plane: normal component of gravity = normal force; parallel component of gravity = static friction.
•Unless the object levitates or crashes through the inclined plane, the normal force always equals the normal component of gravity.
Frictional force is not a fundamental force (like gravitational, strong force, electromagnetic, and weak force). Frictional force is derived from electromagnetic force between charged particles, including electrons, protons, atoms, and molecules, and so cannot be calculated from first principles, but instead must be found empirically. So, when an object on an incline is not moving because of a greater static frictional force than the force down the incline, the object is not moving, so the net force is zero. The net force is not referring to the static frictional force, because it is not zero. It is just that the all of the forces acting on the object is balanced, so net force is zero and the object isn't moving.
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Explain the concept of parallel-plate capacitor.
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■C = Q/V = εA/d
■Greater capacitance is created by a greater charge on plates (Q) for a given voltage (V), greater plate area (A), or smaller distance between plates (d).
■V = Ed, where V is voltage across capacitor, E is electric field between capacitor, and d is the distance between capacitor plates.
In other words, something with a high capacity can store a lot of charge at low voltage. In a parallel plate capacitor, since the charge sits on the surface of the plates, the taller and wider the face of each plate, the more charge each plate will be able to store.
Recall also that voltage is defined by distance (V = Ed). Thus, the farther the plates are separated, the greater the voltage, and the lower the capacitance.
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When presented a mechanics problem...
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• check first to see if you can solve for conservation of energy
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Then the torque is zero
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In general if a force acts at the pivot point or through the pivot point...
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What happens when you put a negative sign on a vector?
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It maintains its magnitude but changes its direction by 180 degrees.
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What is the electric field strength equation in terms of E?
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Electric field strength is a vector quantity; it has both magnitude and direction. The magnitude of the electric field strength is defined in terms of how it is measured. Let's suppose that an electric charge can be denoted by the symbol Q. This electric charge creates an electric field; since Q is the source of the electric field, we will refer to it as the source charge. The strength of the source charge's electric field could be measured by any other charge placed somewhere in its surroundings. The charge that is used to measure the electric field strength is referred to as a test charge since it is used to test the field strength. The test charge has a quantity of charge denoted by the symbol q. When placed within the electric field, the test charge will experience an electric force - either attractive or repulsive. As is usually the case, this force will be denoted by the symbol F. The electric force between two charges is derived from Coulomb's Law and is: F = k*q*Q/r^2, in terms of the test charge and source charge. The electric field is defined as the force per charge on the test charge, or E = F/q. If we use both equations, we get E = k*Q/r^2. The electric field strength is dependent upon the quantity of charge on the source charge (Q) and the distance of separation (r) from the source charge. A charge particle accelerates in an electric field. The force of an electric field is found by F = E/q and E = kq/r^2. Whenever an electric field is constant, as it is with parallel plate capacitors, it's easy to find force because you use that constant and divide by the charge of whatever you're studying. Remember, the electric field always points in the direction of a positive charge.
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What is the electric field strength equation in terms of E?
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An electric field is defined as the electrostatic force per unit charge. The symbol for any electric field is E. E is a vector pointing in the direction of the field and has units of N/C or V/m. For a point charge, the electric field is found by dividing Coulomb's law by q giving: E = kq1/(r^2).
The electric field for a system of point charges is found by summing the fields due to each charge. Remember that E is a vector and you must use vector addition when summing fields.
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How do you find work on a graph?
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area under a P vs. V graph
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If a lever arm is halved, by how much does the torque increase or decrease?
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Torque would decrease by half.
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What is frequency and angular frequency?
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◦Frequency (f): the rate, or how many cycles per second, in Hertz which means cycles per second.
■f = 1/T. Frequency is the number of occurrences of a repeating event per unit time.
■Sometimes, frequency is in rpm (revolutions per minute). rpm = cycles per second x 60.
◦Angular frequency (w): the rate, in how many radians per second.
■w = 2πf which is radians/sec.
■w is also called angular velocity.
w is also equal to the square root of k/m, where k is the constant of Hooke's law, and m is mass in kg. This equation helps you to know what the frequency of something is that is vibrating, such as when you pull an object on a string that vibrates back and forth. k measures how stiff an object is, so that stiffness affects how frequently it vibrates.
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What is frequency and angular frequency?
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Frequency of a wave is the number of wavelengths that pass a fixed point in one second. Hertz is written as 1/s. The period is the number of seconds required for one wavelength to pass a fixed point. When the x-axis is time, the period is from any point on the wave function, to the next point where the function begins to repeat itself.
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The force will go in the opposite direction
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If the charge is negative then which direction will the Force go in relation to an electric field?
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Explain how a ship is held above water and how it can move through water with a small propeller.
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-the fluid conforms its surface to that of the ship so all forces are normal to its surface
-a much smaller force than the ships weight can propel b/c the net force from the ship is not perpendicular to the surface of the water and thus the water provides only temporal resistance
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What is the energy of charged capacitor?
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■U = Q^2/2C = ½QΔV = ½C(ΔV)^2. U is the potential energy of the charged capacitor, Q is charge stored (magnitude of either +Q or -Q on one of the plates), C is capacitance. From the definition of voltage as the energy per unit charge, one might expect that the energy stored on this ideal capacitor would be just QV. That is, all the work done on the charge in moving it from one plate to the other would appear as energy stored. But in fact, the expression above shows that just half of that work appears as energy stored in the capacitor. For a finite resistance, one can show that half of the energy supplied by the battery for the charging of the capacitor is dissipated as heat in the resistor, regardless of the size of the resistor. The battery transports charge from one plate of the capacitor to the other and this energy is stored in the electric field between the plates.
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What is the energy of charged capacitor?
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If we were to graph Q vs. V, the area under the curve would be the product of the charge times voltage or potential energy. The area is a triangle, which is 1/2 base times height or U = 1/2QV.
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What are the two different types of units?
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1. Derived -- those made in terms of other units. 2. Standard -- those which are compared to a standard.
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Is it possible for a force acting over a distance to perform no work?
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yes, if F⊥Δs, then the work done by the force is zero
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