Cheatography

Physics Praxis Cheat Sheet by MsRTischler

Study guide for Physics Praxis 5266

Nature of Science: 15 questions, 12%

 Vector magnitude NO direction Ex= speed, distance Scalar magnitude & Direction. Ex= accele­ration, displa­cement Signif­icant Figures all digits after the first non-zero are signif­icant ex: 0.00410 3 sig figs, 23840100 6 sig figs leading zeros don't count adding round to # with the fewest decimals Accuracy ex:how close results are to the true value Precision how close results are to one another Systematic Error consistent error Accele­ration v/t 1/2gt2 Weight W=mg=mass X gravity Work W=Force x distance

Matter and Energy: 19 questions, 15%

 Bohr model electrons move in fixed orbitals (shells) and not anywhere in between and that each orbit (shell) has a fixed energy Particles alpha= 2p,2n bound beta=high energy, high speed electrons gamma=shortest wavelength electr­oma­gnetic waves Fission breaks releases energy ex. atom smashing Fusion combines releases energy ex. sun Energy transfer radiation= emitted conduction= touch convection= fluids Thermo­dyn­amics 1st law= conser­vation of energy 2nd law= entropy increases 3rd law= A perfect crystal at zero Kelvin has zero entropy Ideal Gas Law Boyle's law PV=nRT pressure and volume of a gas have an inverse relati­onship Kinetic energy energy of motion =1/2mv2 Potential energy stored energy =mgh PE=KE mgh=1/2mv2 mgh=1/2mv+ mg(2R) ME= KE + PE velocity b4 impact: square root (2gh)

Waves: 21 questions, 17%

 Transverse waves motion in which all points on a wave oscillate along paths at right angles to the direction of the wave's advance. Ex Water ripples Longit­udinal waves vibration of medium is parallel to the direction the wave travels and displa­cement of the medium is in the same direction of the wave propag­ation. Ex: sound Mechanical waves an oscill­ation of matter, and transfers energy through a material medium. ex: sound, water Electr­oma­gnetic formed when an electric field couples with a magnetic field. ex. light, gamma Compre­ssion waves the particle motion is in the same direction in which the wave is propag­ating i.e. longit­udinal Doppler effect: the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave moving away= longer toward­s=s­horter Sound Sonic boom= shock waves created when an object travels through the air faster than the speed of sound sound barrier sudden increase in aerody­namic drag that happens when an object approaches the speed of sound Pitch=frequency Loudness=intensity

Waves pt 2: 21 questions, 17% (copy)

 Snell's law: relati­onship between angles of incidence & refraction refraction= the bending of light or sound as it passes through something like a wall (sound) or a window (light). reflection= the throwing back without absorbing it. n1sin01 = n2sin02 change in direction Optics real image= occurs where rays converge virtual image= rays only appear to diverge Polari­zation= division into two sharply distinct opposites Lenses converging= both sides of the lens curve outward it will bend light from distant objects inwards toward a single point, called the focal point convex=refract and converge further from lens the bigger the object appears diverging=both sides of the lens curve inward and light from distant objects will bend outwards. concave=refract and diverge, always smaller + behind lens - in front of lens more lenses, - the focal length

Mechanics: 44 questions, 35%

 Newton's 1st law of inertia: objects at rest remain at rest Newton's 2nd F=ma: the greater the mass the more force needed to accelerate Newton's 3rd every action has an equal and opposite reaction Kepler's 1st all planets move in an elliptical orbit around the sun Kepler's 2nd planets will move slowly far away from the sun, and faster closer to the sun Kepler's 3rd the square of the period of any planet is propor­tional to the cube of the axis of the orbit. Friction force that resists the slidin­g/r­olling of a solid object over another Bernou­lli's principle an increase in speed of a fluid simult­ane­ously with a decrease in pressure or a decrease in the fluid's PE Uniform circular motion centri­petal accele­ration, net force is directed to the center increasing radius decreases force F=m(v2/r)cos0 Rotational motion motion of an object around an axis. w=0/t Harmonic motion F = -kx Hooke's law the force exerted by a spring is propor­tional to its length Collisions elastic- momentum conserved ex. pool balls move apart inelastic- momentum not conserved ex. 2 cars stuck together, move together Centri­petal force increase radius, decrease the force. F=m(v2/r)cos0 Bouyant force F = -pgV the upward force exerted on an object immersed in a fluid Displa­cement D=VT=v­elo­cit­yXtime Vectors add or subtract by placing tip to tail Pascal's principle The pressure at any point in the fluid is equal in all direct­ions. pressure input = pressure output modulus bulk= reaction to squeezing elastic= ratio of stress to strain young= elasticity and length shear= elasticity and stress Pendulums Time=2­pi(­square root (lengt­h/g­rav­ity)) freq (displ­ace­ment) = amplitude sin (ang freq * t)

Electr­icity & Magnetism: 26 questions, 21%

 Coulomb's law F = k(q1q2)/r2 the force of attrac­tio­n/r­epu­lsion between 2 charged bodies is propor­tional to the product of their charges and inversely propor­tional to the square of the distance between them Conductors allows the movement of electrons and ions through. Ex. copper, gold, silver, steel, aluminium & brass have moveable charges Insulators don't allow electric current to pass through, electrical resist­ance. Ex. glass, plastic, rubber, air, & wood Ohm's law V = IR the relati­onship between voltage, current & resistance in an electrical circuit. Biot-S­avart law describes the magnetic field generated by a constant electric current Lorentz force combin­ation of electric and magnetic force on a point charge due to electr­oma­gnetic fields. to determine the direction of the magnetic force on a positive moving charge, point right thumb in the direction of the velocity (v), index finger in the direction of the magnetic field (B), and middle finger will point in the direction of the the resulting magnetic force Ampere's law the sum of the length elements times the magnetic field in the direction of the length element will be equal to the permea­bility times the electric current. Lenz's law direction of the electric current induced in a conductor by a changing magnetic field, the magnetic field created by the induced current opposes changes in the initial magnetic field Kirchoff's laws sum of all currents entering a junction must equal the sum of all currents leaving the junction Electric field the electric force per unit charge Electric potential V = k(q/r) amount of work energy needed per unit of electric charge to move the charge from a reference point to a specific point in an electric field the stronger the field= more potential I=V/R V=IR R=V/I Series one path Rt=R1+ R2+R3.... It= I1 =I2 Vt = V1 + V2 Parallel many paths 1/Rt=1­/R1­+1/­R2... It = I1 + I2 Vt = V1 =V2 decrease resist­ance= decrease length, increase radius total resistance is less than individual Gauss's law how much of something is INSIDE a completely closed surface by measuring how much is flowing out through the sides of that surface. the electric flux Φ across any closed surface is propor­tional to the net electric charge q enclosed by the surface Magnetic field F= qvB sin 0, where q is the magnitude of the charge, B is the magnitude of the magnetic field, v is the speed, and is the angle of the velocity with respect to the field. As increases from 0° to 90°, the force increases.