# MCAT Physics Comprehensive

 Average velocity Vavg = (V1 + V2) / 2 Determining height reached Time to reach peak * average velocity Determining horizontal distance Total time in air * X component of Vinitial Net force = 0 means... No acceleration. Can however have velocity but a = 0 If volume changes, is work being done? Yes Tension is... Vector attributes Has both magnitude and direction. Scalar attributes Has only magnitude Newton's first law The velocity of a body remains constant unless the body is acted upon by an external force. Newton's second law F=ma Newton's third law For every action there is an equal and opposite reaction. Inertia definition The ability of an object to resist a change to its velocity. Center of Mass formula Cmass = (r1m1 + r2m2 + r3m3...)/mtotal r - the displacement vector between a reference point and each vector. Center of gravity At the center of mass. Center of buoyancy The geometric center, irrespective of the center of mass. "Constant Velocity" or " Constant Speed" means No accelerationNo NET forceAll forces sum to zeroNo change in directionThe object is in equilibrium Distance or height traveled formula Distance = rate * time Range (horizontal distance traveled) formula Range = Vx * time When facing projectiles think: Horizontal velocity never changes (ignoring wind resistance)Horizontal acceleration always = 0Vertical acceleration always = 10 m/s2Vertical behavior is always symmetrical (upward = downward)Time in the air depends on the vertical component of velocity only.Range depends on both the vertical and horizontal components. Time is always the same for both the x and y components of the motion. Formula for displacement in projectile motion X = 1/2at2 Formula for final velocity when only height is given V = √(2gh) Formula for "round trip" or total time in air tair = 2V/g V must be the vertical component of initial velocity The effect of surface area on air resistance Greater surface area = more air resistance The effect of shape on air resistance Less aerodynamic = more air resistance The effect of contour on air resistance Rough surface = more air resistance The effect of velocity on air resistance Greater velocity = more air resistance Gravity definition A field that exists between any two objects with mass. Field definition An invisible influence that can exert a force on a mass or charge. Universal Law of Gravitation (force due to gravity) (In space) F = mg (Near earth) Formula for gravity, strength of gravitational field, acceleration due to gravity Gravitational Potential Energy (In space) PE = mgh (Near earth) Friction facts Friction opposes sliding not motion.If there is sliding, it's kinetic friction; if there's no sliding, it's static friction.Static µ is always greater than kinetic µ.Surface area does not increase friction when the mass is the same. Force due to friction formula Ff = µ(s/k)FN Ff = µ(s/k)mgcos Force down an inclined plane formula F = mgsin Normal force on an inclined plane formula FN = mgcos Velocity at the base of an inclined plane Vf = √(2gh) Hooke's Law F = k∆x x - displacementk - spring constant Elastic Potential Energy formula Simple Harmonic Motion formulas T = 2π√(m/k) (mass on a spring) T = 2π√(L/g) (pendulum) T - period (time/wave)m - massk - spring constantL - length of pendulumg - gravity Equililbrium terms Terminal velocityConstant velocityObjects at restBalanced fulcrums or boards on stringsObjects floating in liquid Torque and lever arms T = FT = mgT = Frsin - lever armr - distance between the force and the point of rotation.rsin - always equals , but r = only when = 90˚ Solving for systems in and not in equilibrium Equilibrium - list all the forces and put them equal to one another. Not Equilibrium - list all the forces and add "ma" to the loosing side. Circular motion formula Centripetal vs. Centrifugal If a string is pulling a ball into a circular motion, the string's force on the ball is centripetal and the ball's force on the string is centrifugal. Centrifugal does not exist. Angular motion formulas - angular frequency (rad/s)v - tangential velocity (m/s)r - radius (m)f - frequency (Hz) For the MCAT angular frequency and angular velocity are synonymous. Rotational equilibrium An object is in rotational equilibrium if:1. It is NOT rotataing2. It is rotating with a constant angular velocity/frequency Momentum momentum is inertia increased by velocity and is always conserved (remains constant) in an isolated system. Impulse Impulse = ∆Impulse = m∆vImpulse = Favgt If there is no change in velocity, there can be no impulse.The greater the change in velocity the greater the change in impulse. Elastic Collisions (KE1 + KE2)before + (KE1 + KE2)afterIn elastic collisions momentum and energy are both conserved. Inelastic Collisions m1v1 + m2v2 = m1v1 + m2v2 In inelastic collisions momentum is conserved but energy is not. For perfectly inelastic collisions the equations becomes: m1v1 + m2v2 = (m1 + m2)v3 Stress Force/Area Strain ∆dimension/original dimension Modulus of elasticity (ME) stress/strain Young's modulus - simultaneous pushing or pulling, perfectly lined up with one another.Shear modulus - simultaneous pushing or pulling not perfectly lined up.Bulk modulus - simultaneous compression from all sides. Thermal expansion formula ∆L = Lo∆T T - temperatureL - length in inches - coefficient of thermal expansion Internal energy The energy of internal vibrations of molecules or atoms within a system. Heat energy Energy dissipated as heat. On the MCAT this usually means heat dissipated from a collision. Heat energy and internal energy are almost synonymous. Chemical energy The energy contained within chemical bonds, or the energy stored/released due to the separation and/or flow of electrons. Mechanical energy ME = KE + PE Work formulas W = ∆EnergyW = Fdcos Units - Joules () or () Atmospheric Pressure Force per unit area exerted upon a surface by the weight of the air above that surface in the atmosphere. Fluid Pressure Force exerted by a fluid on a point equal to the density of the fluid times the depth. Gauge Pressure The pressure difference between a system and the surrounding atmosphere. 1 atm equivalents 760 torr760 mmHg101 kPa101,000 Pa14.7 psi General Pressure formula P = F/A Pressure = Force / Area Fluid Pressure formula P = gh (rho) = fluid densityg = gravityh = height of fluid Specific Gravity formula SG = Dsubstance/DH2O D = density Density of water 1000 kg/m31.0 g/cm3 Volume measurements of water 1cm3 = 1mL Mass of water 1L = 1kg 1mL = 1gram For objects floating in fluid, the fraction submerged = The ratio of the density of the object to the density of the liquid. Archimede's Principle The buoyant force is exactly equal to the weight of the displaced fluid. Buoyancy formula Fbuoyant = vg = fluid densityv = volume of displaced fluidg = gravity Apparent Weight The apparent weight of a submerged object is the actual weight minus the buoyant force. The apparent weight gives us 1) the buoyant force and 2) the weight of that volume of fluid. Flow Rate formula Q = AVQ = flowA = cross-sectional area of tube (m2)V = velocity of the fluid (m/s) Application (cardiac output = stroke volume x heart rate) Bernoulli's Equation K = P + gh + 1/2 v2 P = random kinetic energy of the fluid moleculesgh = the gravitational potential energy of the fluid1/2v2 = the energy due to moving fluid moleculesK = a constant Velocity of H2O exiting a spigot formula v = √(2gh) Surface Tension The intensity of intermolecular forces per unit length at the surface of a liquid. Adhesion An attraction between unlike particles. Cohesion An attraction between particles of the same kind. Charge magnitude of an electron e- = 1.6 E-19 C Current flows... From positive (+) to negative (–) Electrons flow... From negative (–) to positive (+) What is current? The flow of eletrons from areas of higher density (where they strongly repel each other) to areas of lower density (where there is less repulsion). Electric Field Field = an invisible influence that can exert a force on a mass or charge. Point Charge Field Equates to "real" gravity or gravity in space. Constant Electric Field Equate to "assumed" gravity or gravity near earth. Electric field equivalent to "g" gravity E - Strength of electric field Electric field equivalent to "G" gravity constant K - constant Electric field equivalent to "h" height r - radius or distance Electric field equivalent to "m" inertial component q - charge Strength of an e-field formula E = V/d E - strength of an electric fieldV - voltaged - distance Voltage for point charge e-field formula V = Kq/r V - voltageK - constantr - radius Voltage formula V = PE/q Voltage is equal to potential energy over charge Resistance formula R = pL/A p - resistivityL - lengthA - cross-sectional area Capacitance formula U = 1/2 CV2 U - PE C - capacitance V - voltage C = Q/V Q - charge Dielectric characteristics InsulatorPolarizableResistorMakes more charge build up on the plates Variables that affect capacitance Plate area (directly related)Plate thickness (no effect)Distance between plates (inversely related)Strength of dielectric (directly related) Capacitor charge vs. time graph Conceptual ideas of a battery Positive terminal has highest electric potential.Electrons build up on negative terminal and move to positive. Conceptual ideas of a resistor There is always a voltage drop across any resistor.Current through a resistor is inversely related to resistance. 2x resistance = 1/2 current. Solving circuits Must be simplified, eg. no more than one of each component.1. Resistors in series: add directly2. Resistors in parallel: add the inverses and take the inverse3. Capacitors in series: add the inverses and take the inverse4. Capacitors in parallel: add directly5. Batteries in series: add directly6. Batteries in parallel: total voltage = the highest voltage of any one of the batteries in parallel Ohm's Law V = IR V - voltageI - currentR - resistance Electric power formula P = IV P - power AC vs. DC Alternating current is created by a generator and can be represented by a sine wave.Direct current is created by a battery. Fmagnet on a charged particle formula F = qvBsin F - force AuthorMaki6tu ID160280 Card SetMCAT Physics Comprehensive DescriptionPhysics Updated2012-08-02T19:23:04Z Show Answers