sat2物理

SAT2

SAT2

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SAT 2

absolute acceleration absolute error absolute motion absolute temperature absolute velocity absolute zero absorption absorptivity accelerated motion acceleration of gravity acceleration accidental error acoustics acting force adjustment aether air pump air table air track alternating current circuit alternating current generator alternating current altimeter ammeter amperemeter ampere Ampere's experiment Ampere's force Ampere's law amperemeter amplitude angle of rotation angular acceleration angular displacement angular velocity anion anisotropy annihilation anode antenna applied physics Archimedes principle area argumentation argument astigmatoscope atomic nucleus atomic physics atomic spectrum atomic structure atom Atwood ' s machine average power average velocity Avogadro constant Avogadro law balance ballistic galvanometer band spectrum barometer basic quantity basic units battery charger battery,accumulator battery beam betatron Bohr atom model boiling point boiling bounce bound charge bound electron branch circuit breakdown brightness buoyancy force calorifics camera capacitance capacitor capillarity cathode ray cathode-ray tube cathode cation cell Celsius scale centre of gravity centre of mass centrifugal force centripetal acceleration centripetal force chain reaction chaos characteristic spectrum charged body charged particle charge circular hole diffraction circular motion classical mechanics classical physics cloud chamber coefficient of maximum static friction coefficient of restitution coefficient of sliding friction coefficient coherent light coil collision component force component velocity composition of forces composition of velocities compression concave lens concave mirror concurrent force condensation condenser conducting medium conductor conservative force field conservative force constant force constant continuous spectrum convergent lens convex lens convex mirror coordinate system coplanar force Corolis force corpuscular property corpuscular theory Coulomb force coulomb Coulomb's law counter creation creepage crest critical angle critical resistance critical temperature crystal current density current element current source current strength curvilinear motion cyclotron damped vibration damping Daniell cell data processing data decay definition of ampere defocusing density derived quantity derived unit dielectric diffraction pattern diffraction diffuse reflection digital timer dimensional exponent dimension diode diopter direct current, DC direct impact direct measurement discharge disorder dispersion displacement divergent lens Doppler effect double slit diffraction driving force dry cell echo eddy current effective value elastic body elastic force elasticity electric charge electric circuit electric corona electric energy electric field electric field intensity electric field line electric flux electric leakage electric neutrality electric potential electric potential difference electric potential energy electric power electric quantity electrification electrification by friction electrified body electrode electrolysis electrolyte electromagnetic damping electromagnetic induction electromagnetic radiation electromagnetic wave electromagnetic wave spectrum electromagnetism induction phenomenon electromagnet electrometer electromotive force electron electron beam electron cloud electron microscope electron volt electroscope electrostatic equilibrium electrostatic induction electrostatic screening elementary charge energy energy level equilibrium equilibrium condition equilibrium of forces equilibrium position equilibrium state equivalent source theorem erect image

error ether evaporation excitation excitation state experiment experimental physics external force eyepiece far sight Faraday cylinder Faraday law of electromagnetic induction Faraday's law of electromagnetic induct farad () film interference final velocity first cosmic velocity fission fixed-axis rotation flotation balance fluid focal length focusing focus force forced vibration fractal free charge free electron free period freezing point frequency friction force fusion galvanometer gas general physics generator good conductor gravitation gravity gravitational potential energy gravity field ground earth ground state ground wire hadron half life period heat heat transfer henry hertz () Hooke law humidity hydrogen hypothesis ice point ideal gas image image distance image height imaging imperfect inelastic collision impulse incident angle incident ray indirect measurement induced electric current induced electric field induction current induction electromotive force induction motor inertia inertial force inertial system infrared ray infrasonic wave initial phase initial velocity input instantaneous power instantaneous velocity instrument insulated conductor insulating medium insulator intensity of sound interference interference fringe interference pattern interferometer internal energy internal force internal resistance intonation inverted image invisible light ion beam ionization irreversible process isobaric process isobar isochoric process isothermal isothermal process isotope isotropy joule Joule heat Joule law Joule' law Kepler law kinematics kinetic energy Laplace's equation laser law law of conservation of angular momentum law of conservation of energy law of conservation of mass law of conservation of mechanical energy law of conservation of momentum law of electric charge conservation Le Systme International d ` Unit s (SI) lead length lens lens formula Lenz's law lepton Light ray light source light wave lightning rod light line spectrum lines of current lines of force of electric field liquefaction liquefaction point liquid longitudinal wave loop Lorentz force luminous intensity magnetic field magnetic field intensity magnetic field line magnetic induction flux magnetic induction magnetic induction line magnetic material magnetic needle magnetic pole magnetics magnetism magnetization magnet magnification magnifier manometer mass mass defect mass-energy equation matter matter wave Maxwell's equations mean speed mean velocity measurement mechanical energy mechanical motion mechanical vibration mechanics medium melting fusion melting point metre rule microdetector micrometer caliper microscope microscopic particle mirror reflection mirror mixed unit system modern physics molar volume molecular spectrum molecular structure moment of force momentum of electromagnetic field momentum motor multimeter musical quality N pole natural frequency natural light negative charge negative crystal negative ion negative plate network neutralization neutron newton Newton first law Newton second law Newton third law nonequilibrium state north pole nucleus force nucleus of condensation object object distance object height objective observation Oersted's experiment ohm Ohm law ohmmeter Ohm's law open circuit optical bench optical centre of lens optical fiber optical glass optical instrument optical lever optical path difference optical path () optically denser medium optically thinner medium optics orbit order oscillograph output overweight parallel connection of condensers parallelogram rule parallel-resonance circuit parameter particle Pascal law path peak pendulum penumbra perfect conductor perfect elastic collision perfect inelastic collision periodicity period periscope permanent magnet permittivity of vacuum permittivity phase phenomenon photocurrent photoelectric cell photoelectric effect photoelectron photography photon physical balance physical quantity physics piezometer pitch Planck constant plasma point charge polarization polarized light polycrystal poor conductor positive charge positive crystal positive ion positive plate positron potential energy potentiometer power pressure primary coil principle of constancy of light velocity prism projectile projectile motion projector proton pulley pulley block quantity of heat quantization quantum quantum mechanics quantum number

radar radioactive source radius of gyration random motion range rated voltage reacting force real image real object reasoning recoil rectilinear motion reference frame reference system reflected angle reflected ray reflection coefficient reflection law reflectivity refracted angle refracted ray refraction law refraction coefficient refractive index relative acceleration relative error relative motion relative velocity relativity resistance resistance box resistivity resistor resolution of force resolution of velocity resonance resonant frequency resultant force resultant velocity reversibility of optical path reversible process rheostat right-hand screw rule rocker rotating magnetic field rotation Rutherford scattering Rutherford -particle scattering experiment S pole saturation scalar scalar field scanner second cosmic velocity selective absorption self-induced electromotive force self-inductance self-induction phenomenon semiconductor semi-transparent film sensitive galvanometer sensitivity sensitometer sensor series connection of condensers series-resonance circuit short circuit short sight shunt resistor significant figure simple harmonic motion (SHM) simple harmonic wave simple pendulum single crystalmonocrystal single slit diffraction sinusoidal alternating current sinusoidal current sliding friction slit solar cell solenoid solidification solidifying point solid solution solvation sonar sound source sound velocity sound wave sound source south pole space spark discharge special relativity specific heat capacity spectacles spectral analysis spectral line spectrograph spectrography spectroscopy spectrum speed spherical mirror spontaneous radiation spring balance stability stabilized current supply stabilized voltage supply standard atmospheric pressure standard cell standing wave static friction stationary state steady current steady current source steady voltage source steam point stiffness stimulated radiation stop watch sublimation superconductivity superconductor superposition principle of electric field superposition theorem supersaturation supersonic speed supersonic wave supply transformer surface resistance switch system of concurrent forces system of particles system of units systematic error telescope temperature tension the law of gravity theorem theorem of kinetic energy theorem of momentum theoretical physics theory thermal capacity thermal equilibrium thermal motion thermal transmission thermodynamic scale of temperature thermodynamic temperature thermometer thermometric scale thermonuclear reaction thick lens thin lens third cosmic velocity three-phase alternating current time timer torsion balance total reflection trajectory transformer transistor transition translation transmission line transmissivity transverse wave triboelectrification triode trough tuning fork turbulent flow ultrasound wave ultraviolet ray umbra undulatory property uniform dielectric uniform motion unit unit system universal constant universal gravitation universal meter vacuum tube vacuum value of amplitude vaporization variable vector velocity of light velocity verification vernier vernier caliper vibration viewing angle viewing field virtual image virtual object virtual value visibility visible light voltage voltage division circuit voltaic cell voltmeter voltmeter-ammeter method volt volume vortex electric field watt wave equation wave theory wavelength wave-particle dualism wave weight weightlessness white light work work function X-ray X Young experiment zero line -decay -particle -ray -decay -ray -decay -ray

SAT2(1)


SAT2,SAT

SAT IIPhysics Formulas - MechanicsKinematics Formulas

The Kinematic Equations apply to one-dimmensional motion with costant acceleration from point 1, situated d1 from a point of reference to point 2, situated d2 from the same point of reference. v1 is the velocity at point 1 and v2 is the velocity at point 2.v2 = v1 + atd2 = d1 + (v1 + v2)t/2d2 = d1 + v1t + at2/2d2 = d1 + v2t - at2/2v22 = v12 + 2a(d2 - d1)

Average velocity: vav = d/tAverage acceleration: aav = v/t

Rotational kinematics equations with constant angular acceleration:2 = 1 + t2 = 1 + (1 + 2)t/22 = 1 + 1t + t2/22 = 1 + 2t - t2/222 = 12 + 2(2 - 1)

Average angular velocity: av = /tAverage angular acceleration: av = /tFrequency: f = /2Period: T = 2/

Relations between angular and linear variables:l = rv = ra = r

Dynamics Formulas

Pressure: P = F/ANewton's Second Law: F = maForce of kinetic friction: Ff = NHooke's Law: F = -kxCentripetal Force: Fc = mv2/RCentripetal acceleration: ac = v2/R

Work, Energy, Conservation Laws Formulas

Work: W = F d = Fdcos()Potential Energy: PE = mghKinetic Energy: KE = mv2/2Mechanical Energy: E = KE + PEInstantaneous Power: P = FvThe Work-Energy Theorem: W = KE

Gravitation Formulas

Newtonian gravity formula: Fg = GmM/R2Kepler's Third Law: T2/a3 = ct.

SAT IIPhysics Formulas - ThermodynamicsHeat added or emoved: Q = mcTChange in Internal Energy: U = Q - WBoyle's Law: P1V1 = P2V2Charles's Law: V1/T1 = V2/T2Efficiency of a heat engine(%): E = (W/Qhot)100

SAT IIPhysics Formulas - Waves and Optics

Snell's Law: n1sin(1) = n2sin(2)Wave speed: v = fVelocity of light: v = c/nMagnification: m = -di/doLaw of Reflection: reflection = incidenceMirror and lens equation: 1/d1 + 1/d1 = 1/f

SAT IIPhysics Formulas - Modern Physics

The energy of a photon: E = hfMatter wavelength: = h/pRelativistic factor: 2 = 1/(1 - v2/c2) De Broglie Wavelength: = h/(mv)Half life of radioactive material: Thalf = ln(2)/Mass energy equivalence: E = moc2

SAT IIPhysics Formulas - Electricity and Magnetism

Electric Fields and Forces Formulas

Coulomb's Law: F = kq1q1/r2Electric field of a charge q: E = kq/r2Work done by electric field: W = qEdElectric field between two metallic plates: E = V/d

DC Circuits Formulas

Ohm's Law: V = IRPower dissipated in a resistor: P = IV = V2/R = RI2Resistance: R = l/AEquivalent resistance of series resistors: Rs = R1 + R2 +...Equivalent resistance of parallel resistors: 1/Rp = 1/R1 + 1/R2 +...Equivalent capacitance of series capacitors: 1/Cs = 1/C1 + 1/C2 +...Equivalent capacitance of parallel capacitors: Cp = C1 + C2 +...

Magnetic Fields and Forces Formulas

Magnetic force on a moving charge: F = q(v x B) = qvBsin()Magnetic force on a current carrying wire: F = IlBsin()Magnetic field created by a current: B = (o/2)(I/r)Faraday's Law: E = -d/dt

SAT2:


SAT2Two-Dimensional Motion with Uniform Acceleration

If youve got the hang of 1-D motion, you should have no trouble at all with 2-D motion. The motion of any object moving in two dimensions can be broken into x- and y-components. Then its just a matter of solving two separate 1-D kinematic equations.

The most common problems of this kind on SAT II Physics involve projectile motion: the motion of an object that is shot, thrown, or in some other way launched into the air. Note that the motion or trajectory of a projectile is a parabola.

If we break this motion into x- and y-components, the motion becomes easy to understand. In the y direction, the ball is thrown upward with an initial velocity of and experiences a constant downward acceleration of g = 9.8 m/s2. This is exactly the kind of motion we examined in the previous section: if we ignore the x-component, the motion of a projectile is identical to the motion of an object thrown directly up in the air.

In the x direction, the ball is thrown forward with an initial velocity of and there is no acceleration acting in the x direction to change this velocity. We have a very simple situation where and is constant.

SAT II Physics will probably not expect you to do much calculating in questions dealing with projectile motion. Most likely, it will ask about the relative velocity of the projectile at different points in its trajectory. We can calculate the x- and y-components separately and then combine them to find the velocity of the projectile at any given point:

Because is constant, the speed will be greater or lesser depending on the magnitude of . To determine where the speed is least or greatest, we follow the same method as we would with the one-dimensional example we had in the previous section. That means that the speed of the projectile in the figure above is at its greatest at position F, and at its least at position C. We also know that the speed is equal at position B and position D, and at position A and position E.

The key with two-dimensional motion is to remember that you are not dealing with one complex equation of motion, but rather with two simple equations.

SAT2


SAT II:Format of SAT II Physics

SAT II Physics is a one-hour-long test composed of 75 questions anddivided into two parts. You can answer questions in any order you like,though youre less likely to accidentally leave a question out if you answer them in the order in which they appear. Part Aclassification questionstakes up the first 12 or 13 questions of the test, while PartBfive-choice completion questionstakes up the remaining 62 or 63questions.

Part A: Classification Questions

Classification questions are the reverse of normal multiple-choice question: they give you the answers first andthe questions second. Youll be presented with five possible answerchoices, and then a string of two to four questions to which thoseanswer choices apply. The answer choices are usually either graphs orthe names of five related laws or concepts. Because they allow forseveral questions on the same topic, classification questions will askyou to exhibit a fuller understanding of the topic at hand.

The level of difficulty within any set ofquestions is generally pretty random: you cant expect the firstquestion in a set to be easier than the last. However, each set ofclassification questions is generally a bit harder than the one thatcame before. You should expect questions 1113 to be harder thanquestions 14.

Classification Question Example

Directions: Each set oflettered choices below refers to thenumbered questions immediatelyfollowing it. Select the one letteredchoice that best answers eachquestion and then blacken thecorresponding space on the answer sheet.A choice may be used once, morethan once, or not at all in each set.Questions 13

A boy throws a ball straight up in the air and then catches it again.1. Which of the above graphs best represents the balls position with respect to time?2. Which of the above graphs best represents the balls velocity with respect to time?3. Which of the above graphs best represents the balls acceleration with respect to time?

Explanation

You can usually answer classification questionsa bit more quickly than the standard five-choice completion questions,since you only need to review one set of answer choices to answer aseries of questions.

The answer to question 1 is B. The balls position with respect to time can be expressed by the equation y = 1/2 gt2, where g is the downward, acceleration due to gravity. As we can see, the graph of y against tis an upside-down parabola. In more intuitive terms, we know that, overtime, a ball thrown in the air will rise, slow down, stop, and thendescend.

The answer to question 2 is E. Theacceleration due to gravity means that the velocity of the ball willdecrease at a steady rate. On the downward half of the ballstrajectory, the velocity will be negative, so E, and not A, is the correct graph.

The answer to question 3 is D. Theacceleration due to gravity is constant throughout the ballstrajectory, and since it is in a downward direction, its value isnegative.

Dont worry if the question confused you and theexplanations didnt help. This material and more will be covered inChapter 2: Kinematics. This was just an exercise to show you how aclassification question is formatted.

Part B: Five-Choice Completion Questions

These are the multiple-choice questions we allknow and love, and the lifeblood of any multiple-choice exam. You knowthe drill: they ask a question, give you five possible answer choices,and you pick the best one. Got it? Good. An example appears below.

While youll often find two or three questionsin a row that deal with the same topic in physics, there is no pattern.You might find a question on modern physics followed by a question ondynamics followed by a question on optics. However, there is a generaltendency for the questions to become more difficult as you progress.

Five-Choice Completion Question Example

Directions: Each of thequestions of incomplete statementsbelow is followed by five suggestedanswers or completions. Select theone that is best in each case andthen fill in the corresponding oval onthe answer sheet.

1. A gas in a closed container is steadily heated over a period of time. Which of the following statements is true of this process?(A)The average kinetic energy of the gas molecules decreases(B)The mass of the container increases(C)The pressure exerted by the gas on the walls of the container increases(D)The gas changes phase into a liquid(E)The specific heat of the gas decreases

Explanation

The answer to this question is C. The key lies in remembering the ideal gas law: PV = nRT. According to this formula, an increase in temperature is accompanied by an increase in pressure. Ais wrong, since the average kinetic energy of gas molecules correspondsto their temperature: if the temperature increases, so does the averagekinetic energy of the molecules. B is wrong because were dealing with a closed container: the mass cannot either increase or decrease. D is wrong because a gas must be cooled, not heated, to change phase into a liquid. Finally, Eis wrong because the specific heat of any substance is a constant, andnot subject to change. Well touch on all this and more in Chapter 9:Thermal Physics.

SAT2


SAT2Content of SAT II Physics

Math and physics go hand in hand, right? You might be surprised, then,to learn that you arent allowed to use a calculator on SAT II Physics.The math required of you never goes beyond simple arithmetic andmanipulation of equations. You have, on average, 48 seconds to answereach question, and the people at ETS realize that isnt enough time todelve into problems involving simultaneous equations or complextrigonometry. Theyre more interested in testing your grasp of thebasic concepts of physics. If youve grasped these concepts, yourweakness in math isnt going to hurt you.

ETS breaks down the concepts you need to know for the test into six categories:

TopicPercentage of the Test

Mechanics3438%

Electricity and Magnetism2226%

Waves1519%

Heat, Kinetic Theory, and Thermodynamics812%

Modern Physics812%

Miscellaneous24%

While these categories are helpful, they arealso very broad. You may be a whiz with waves but a loser with lenses,and want to know how much of the waves portion of the test will bedevoted to optics. To help you out, weve broken the test down evenfurther so that youll know exactly where to expect to feel thesqueeze. (These figures are only approximations, and may vary from testto test.)

Topic% of the TestNumber of Questions

Mechanics3438%2529

Vectors2%12

Kinematics6%45

Dynamics10%78

Work, Energy, and Power6%45

Special Problems in Mechanics5%34

Linear Momentum2%12

Rotational Motion1%01

Circular Motion and Gravitation4%24

Thermal Physics812%610

Heat and Temperature4%24

Kinetic Theory and Ideal Gas Laws23%12

Laws of Thermodynamics1%02

Heat Engines23%12

Electricity & Magnetism2226%1620

Electric Fields, Forces, Potential10%78

Magnetic Fields and Forces6%45

Electromagnetic Induction1%1

Circuits and Circuit Elements6%45

Waves1519%1115

Waves10%78

Optics7%56

Modern Physics812%69

Special Relativity12%12

Atomic Models3%23

Quantum Physics2%12

Nuclear Physics3%23

Miscellaneous24%13

Graph Analysis12%02

Equation Manipulation0.51%01

Significant Digits and Lab Skills0.51%01

The chapters of this book are organizedaccording to these categories. If a physics topic is not in this book,you don't need to know it. Here's some other helpful information:

You need to know: the formulas expressing physical relationships (such as F = ma), how to manipulate equations, how to read a graph

You don't need to know: trig identities, calculus, three-dimensional vectors and graphs, physical constants (such as G = 6.671011 Nm2 kg2)

SAT1


SAT SAT Physics Practice Test One

Question 1:

An object of mass m moving with a velocity v collides with another object of mass 2m. The two objects stick together and they collide with a third object of mass 3m. After the second collision the three objects move together at the same speed. What is the velocity of the three objects after the second collision?

v/12v/6v/3v/2v

Question 2:An electric motor accelerates its rotation with a constant angular acceleration of 2 rad/s2 until it reaches a frequency of f = 10/ Hz. If the motor starts from rest, how long does it take to reach frequency f?

6s10ss12s15s

Question 3:Two satellites orbit the earth at radii r1 and r1. What is the ratio of the velocities of the two satellites?

Question 4:250J of heat are added to a gas in a cylindrical container and then the gas does 120J of work on the top and bottom walls of the cylinder. What is the change in internal energy for the gas?

0J120J130J250J-120J

Question 5:

Three point charges of charge +Q are placed as shown above. At what point will a negative charge experience a force toward the bottom of the page?

ABCDE

Question 6:Resistor R1 = 5 and resistor R2 = 10 are connected in series to a voltage source E = 60V. What is the ratio between the power dissipation in R2 and the power dissipation in R1?

12345

Question 7:Resistor R1 = 4 and resistor R2 = 6 are connected in series. If the tolerance of R1 is 1% and the tolerance of R2 is 2%, what is the tolerance of the equivalent resistor R?

.8%1%1.6%2%3%

Question 1 solution:

According to the law of conservation of momentum,mv = (m + 2m)v1 and,(m + 2m)v1 = (m + 2m + 3m)v2, where v1 and v2 are the speed after the first and after the second collision.In conclusion, mv = 6mv2 and v2 = v/6.


t = / = 2f / where is the angular speed and is the angular acceleration.t = 2(10/) / 2t = 10s.


We equate the formulas for gravitational force and centripetal force:mv2/r = GmM/r2

r = radius of the orbit;m = mass of satellite;M = mass of planet;v = speed of satellite;

v12 = GM/r1v22 = GM/r2


According to the First Law of Thermodynamics, the change in internal energy is equal to the change in heat plus the work done on the system.U = Q + W = 250J - 120J = 130J.


A and D are the only points that have the horizontal component of the force equal to zero.A negative charge experiences a force toward the bottom of the page in point A and towards the top of the page in point B.(a) is the correct answer.


P2 = R2I2P1 = R1I2We divide the 2 equations and,P2/P1 = R2/R1P2/P1 = 100/50P2/P1 = 2


R1(1 + t1) + R2(1 + t2) = R(1 + t),We also know that R1 + R2 = R.We substract the second equation from the first equation:R1t1 + R2t2 = Rt,t = (R1t1 + R2t2)/Rt = (41% + 62%)/10t = 1.6% is the tolerance of the series resistor combination. SAT2


SAT SAT Physics Practice Test Two

Question 1:

Five particles charged with the same charge +q move with the same speed v in a magnetic field B, as shown above. Which particle experiences the highest magnetic force?

ABCDE

Question 2:Two wires of circular cross-sectional areas have resistances R1 and R2.If 1 = 22, l1 = 2l2 and r1 = 2r2, what is the ratio R1/R2? 1, 2 are the resistivities of the two wires,l1, l2 are the lengths of the two wires,r1, r2 are the radii of the two wires.

11/21/424

Question 3:

Two wires carry identical currents I, as shown above. At which point is the magnetic field the strongest?

ABCDE

Question 4:

Two metallic bars slide along metallic rails at speeds v1 = .1m/s and v2 = .2m/s as shown above. The bar and the rails are situated in a magnetic field of 4T. What is the induced voltage in the bar and rails?

20mV30mV40mV120mV150mV

Question 5:A police car with its siren on travels at a speed v1 toward a person. The frequency of the siren is f1 and the person hears the sound at a frequency f2. If vs is the speed of sound, v1 =

vsf2/f1vs(1 - f2/f1)vs(f1/f2 - 1)vs(1 - f1/f2)vs(f2/f1 - 1)

Question 6:Violet light has a wavelength of 400nm. What is its frequency, if the speed of light is 3108?

510147.5101410152101551015

Question 7:The activity of a radioactive sample at time t = 0s is A0 and the activity of the same radioactive sample at time t1 is A1. What is the decay constant of the sample?

[ln(A1/A0)]/t1[ln(A0/A1)]/t1[ln(A1 - A2)]/t1[ln(A1/A0)]t1e(A1/A0)t1

SAT2

Question 1:

Five particles charged with the same charge +q move with the same speed v in a magnetic field B, as shown above. Which particle experiences the highest magnetic force?

Solution: The magnetic force experienced by a moving particle is given by the formula F = q(v x B). We can maximize F by ensuring that the speed and the magnetic field are perpendicular to one another. Particule A is the correct answer.

Question 2:

Two wires of circular cross-sectional areas have resistances R1 and R2.If 1 = 22, l1 = 2l2 and r1 = 2r2, what is the ratio R1/R2? 1, 2 are the resistivities of the two wires,l1, l2 are the lengths of the two wires,r1, r2 are the radii of the of the cross-sectional areas of the two wires.

Solution: R1 = l11/A1 = 1l1/(r12) R2 = 2l2/(r22) = (1/2)(l1/2)/(r12/4) = 1l1/(r12)

R1/R2 = 1.

Question 3:

Two wires carry identical currents I, as shown above. At which point is the magnetic field the strongest?

Solution: Points D and B are situated at equal distance from the two wires and the magnetic field is 0 at these points. As the magnetic fields created by the two currents have opposite directions at points A, C and E, the strongest magnetic field will be at point A, because the component generated by the "horizontal" current is much lower than the one created by the "vertical" one.

Question 4:

Two metallic bars slide along metallic rails at speeds v1 = .1m/s and v2 = .2m/s as shown above. The bar and the rails are situated in a magnetic field of 4T. What is the induced voltage in the bar and rails?

Solution: e = -d/dt = -BdA/dtdA/dt = l(dx/dt) = l(v1 + v2)The induced voltage in the bar is Bl(v1 + v2) = 120mV.

Question 5:A police car with its siren on travels at a speed v1 toward a person. The frequency of the siren is f1 and the person hears the sound at a frequency f2. If vs is the speed of sound, v1 =

Solution: The frequency heard by the person is given by the formula:f2 = [vs/(vs - v1)]f1f2vs - f2v1 = f1vsv1 = vs(f1/f2 - 1)

Question 6:Violet light has a wavelength of 400nm. What is its frequency, if the speed of light is 3108?

Solution: f = c/ = 3108/40010-9 = 7.514Hz.

Question 7:The activity of a radioactive sample at time t = 0s is A0 and the activity of the same radioactive sample at time t1 is A1. What is the decay constant of the sample?

Solution: A1 = A0et1A1/A0 = et1 = [ln(A1/A0)]/t1

SAT3


SAT SAT Physics Practice Test Three

Question 1:

What is the magnitude of the vector 3A - B in the figure above?

A.3 B.4 C.5 D.2 E.6

Question 2:

The graph above shows the acceleration of a particle. At t = 0s, the speed of the particle is 1m/s. What is the speed of the particle at t = 4s?

11 m/s9 m/s19 m/s13 m/s10 m/s

Question 3:

Forces F1 and F2 in the figure above act on a block of mass m = 10kg that moves on a frictionless surface. What is the acceleration of the block?

1 m/s1.5 m/s2 m/s2.5 m/s3 m/s

Question 4:

A block of mass m is moving down an inclined plane with a decreasing speed. The coefficient of friction between the block and the plane is . Which of the following statements is true?

sin() < sin() > cos() < cos() > tan() <

Question 5:When a car's kinetic energy increases 9 times, what happens with its speed?

increases 9 timesincreases 3 timesdecreases 9 timesdecreases 3 timesremains constant

Question 6:

An object of mass 4kg is attached to a spring. The equilibrium position of the object is .4m from the point where the spring exerts no force on the object. What is the spring constant, k?

10 N/m80 N/m100 N/m150 N/m200 N/m

Question 7:

An object of mass 10kg sitting on a frictionless horizontal plane is moved from a stationary state by the force shown above. What is the velocity of the object at time t = 5s?

2.5 m/s3 m/s4 m/s5 m/s6 m/s

SAT2

Question 1:

What is the magnitude of the vector 3A - B in the figure above?

Solution:

The magnitude of the vector 3A is 3 and the magnitude of vector B is 4. The angle between vectors 3A and B is 90o. According to the Pythagorean theorem, the magnitude of 3A - B is 5.

Question 2:

The graph above shows the acceleration of a particle. At t = 0s, the speed of the particle is 1m/s. What is the speed of the particle at t = 4s?

Solution: At t = 2s, the speed of the particle is v2s = v0s + 2m/s22s = 5m/s.At t = 4s, the speed of the particle is v4s = v2s + 3m/s22s = 11m/s.

Question 3:

Forces F1 and F2 in the figure above act on a block of mass m = 10kg that moves on a frictionless surface. What is the acceleration of the block?

Solution: F1cos(60o) + F2cos(60o) = ma201/2 + 301/2 = 10a25 = 10aa = 2.5m/s2

Question 4:

A block of mass m is moving down an inclined plane with a decreasing speed. The coefficient of friction between the block and the plane is . Which of the following statements is true?

Solution: mg sin() - mg cos() = aThe speed is decreasing so a < 0. This means thatmg sin() - mg cos() < 0mg sin() < mg cos()tan() <

Question 5:When a car's kinetic energy increases 9 times, what hapens with its speed?

Solution: The car's initial kinetic energy is Ei = mvi2/2 and the final kinetic energy is Ef = mvf2/2.Ef/Ei = (vf/vi)2(vf/vi)2 = 9vf/vi = 3

Question 6:

An object of mass 4kg is attached to a spring. The equilibrium position of the object is .4m from the point where the spring exerts no force on the object. What is the spring constant, k?

Solution:F = kx mg = kxk = mg/xk = 40N/.4mk = 100N/m

Question 7:

An object of mass 10kg sitting on a frictionless horizontal plane is moved from a stationary state by the force shown above. what is the velocity of the object at time t = 5s?

Solution: The area under a force versus time graph gives us the impulse given to the object.p = 10/2 + 30 + 10/2 = 40 kg m/sv = p/mv = 4 m/s

sat2物理

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