Introduction to SAT II Physics - FreeExamPapers

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Permanent Magnets Like all other materials, permanent magnets are made up of atoms that have electrons orbiting a nucleus of protons and neutrons. In moving around the nucleus, these electrons create miniscule magnetic fields. In most materials, these tiny fields all point in different random directions, so the bulk material does not have a magnetic field. But in permanent magnets, the fields are all lined up together, and so the material is magnetized. Materials, like iron, that can be magnetized, are called ferromagnetic. There are two other types of magnetic materials: If a nonferromagnetic material is attracted by a magnet, it is called paramagnetic. The atoms in an paramagnet line up in the direction of an external field. If a nonferromagnetic material is repelled by a magnet, it is called diamagnetic. The atoms in a diamagnet line up against an external field. Magnetic Field Lines Permanent magnets—and electromagnets—have positive and negative poles, often called “north” and “south,” respectively. Like electric field lines, magnetic field lines go from the positive, or north, pole, toward the negative, or south, pole. For example, the magnetic field of a bar magnet looks like this: A horseshoe-shaped magnet creates a magnetic field like this: It is possible to do a nifty experiment to see these magnetic field lines by scattering iron fillings around a permanent magnet—the filings will move to trace the lines. The Earth’s Magnetic Field 246
The Earth itself acts like a huge bar magnet. The presence of a magnetic field about the Earth allows us to use compasses that point northward, and creates a spectacular aurora over the northern and southern skies. But the magnetism of the Earth is quite complicated, and is still an active subject of research for geologists, so let us turn to the simpler cases of idealized charges and constant magnetic fields. Magnetic Force on Charges The questions on magnetism that you’ll find on SAT II Physics will deal for the most part with the reciprocal relationship between magnetic fields and moving charges. Generally, these questions will expect you to predict the motion of a charge through a magnetic field, or to calculate the magnitude of the magnetic force or magnetic field strength necessary to move a charge in a certain manner. Calculating Magnetic Force A magnetic field exerts a force on a moving charge. Given a magnetic field, B, and a charge, q, moving with velocity, v, the force, F, on the charge is: Magnetic field strength is measured in teslas (T), where 1 T = 1 N/A · m. You’ll notice that the force on a moving particle is calculated as a cross product of the particle’s velocity and the magnetic field’s strength. You can determine the direction of the vector by using the right-hand rule as follows: point the fingers of your right hand in the direction of the velocity vector and then curl them around to point in the direction of the magnetic field vector. The direction in which your thumb points gives you the direction of the vector. However, though q is a scalar quantity, it can affect the direction of the force vector. If q has a negative value, then has a negative value, and so the force vector will point in a direction opposite from what the right-hand rule might tell you. You can calculate the magnitude of the magnetic force without using the right-hand rule, so long as you know the angle, , between the velocity vector and the magnetic field vector: The sin term is important, because it lets us see very quickly that there is no force if a charge moves parallel to a magnetic field, and that the greatest force occurs when a charge moves perpendicular to the magnetic field. EXAMPLE 247
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SATII PHYSICS (FROM SPARKNOTES.COM)
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The Good • Because SAT II Subject
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Which SAT II Subject Tests to Take
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After grumbling, however, you still
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Waves 15-19% 11-15 Waves 10% 7-8 Op
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negative, so E, and not A, is the c
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including them anyway because it’
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Two positively charged particles, o
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will a visual representation reliev
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Physics Hint 6: Be Flexible Knowing
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There are a number of ways to label
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Adding Parallel Vectors If the vect
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The result of multiplying A by c is
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neither parallel nor perpendicular.
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Suppose the hands on a clock are ve
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Vector Addition Practice Questions
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2. A The vector 2A has a magnitude
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path, Alan has traveled a much grea
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school student called Andrea. Andre
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centimeters to the left of its star
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We can learn two things about the a
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Acceleration vs. Time Graphs After
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The variable represents the object
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Note that there are certain conveni
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1. . An athlete runs four laps of a
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10. . A woman runs 40 m to the nort
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We know the total distance the spri
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Principles of Natural Philosophy. I
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The component form of Newton’s Se
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e in the direction. And since the s
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which reflects its resistance to be
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In the diagram above, the weight an
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A student pushes a box that weighs
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1. . Each of the figures below show
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7. . In the figure above, a person
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Since the block is motionless, the
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When we are told that a person push
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EXAMPLE A water balloon of mass m i
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The graph above plots the force exe
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Though energy is always measured in
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there is a negative amount of work
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smallest. The answer to question 3
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Mechanical Energy Average Power Ins
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to a height of 8 m over a time of 4
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8. C When the book reaches the pers
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determining what those right number
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the ground. The system is initially
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calculators, you almost certainly w
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and minimize M.” With such a ques
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2. WHAT IS THE ACCELERATION OF THE
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Adding these two equations together
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force of friction: . Using Newton
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m, placed on a frictionless surface
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Frequency is given in units of cycl
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of the spring due to the gravitatio
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The oscillation of a pendulum is mu
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Velocity Calculating the velocity o
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Practice Questions 1. . Two masses,
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7. . An object of mass 3 kg is atta
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Since the system is in equilibrium,
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velocity, v. Linear momentum is den
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Conservation of Momentum If we comb
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As we might expect, the final veloc
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A pool player hits the eight ball,
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two-dimensional collision is effect
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For a System of Two Particles For a
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At the front end of the boat, the f
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4. . A scattering experiment is don
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1. B The athlete imparts a certain
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7. E Momentum is conserved in this
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The diver’s translational motion
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30 π/6 45 π/4 60 π/3 90 π/2 180
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elative position to one another. As
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acceleration given its angular velo
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To find the direction of a rigid bo
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A student exerts a force of 50 N on
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The torque that produces the angula
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The masses in the figure above are
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an object sliding down a frictionle
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Velocity Average Angular Accelerati
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3. . What is the direction of the a
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1. D An object that experiences 120
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At the top of the incline, the disk
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from a Latin word meaning “center
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Newton’s Law of Universal Gravita
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when you are beneath the surface of
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EXAMPLE A satellite of mass is laun
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Kepler’s Laws After poring over t
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Practice Questions Questions 1-3 re
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8. . A satellite orbits the Earth a
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Circumference and radius are relate
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learn how heat is transferred from
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heat, like rubber, have a high spec
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Just as specific heat tells us how
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Conduction is the transfer of heat
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Effectively, this equation tells us
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the way that it does. The Laws of T
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Page 201 and 202: Asphalt, like most materials, has a
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Page 207 and 208: will move in the opposite direction
Page 209 and 210: Work The work done to move a charge
Page 211 and 212: Much like gravitational potential e
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Page 219 and 220: Voltage The batteries we use in fla
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Page 225 and 226: However, each resistor causes a vol
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Page 229 and 230: Consider again the circuit whose to
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Page 241 and 242: 4. . Two resistors, and , are ident
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Page 259 and 260: 1. B To solve this problem, it is h
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Page 265 and 266: Next, let’s calculate the flux th
Page 267 and 268: Remember that field lines come out
Page 269 and 270: Magnetic Flux Faraday’s Law / Len
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Page 279 and 280: other. The principle of superpositi
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Since we know that the ratio of / i
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The four basic kinds of optical ins
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You can test all this yourself with
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Because is a positive number, we kn
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As the diagram shows us, and as the
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At any point P on the back screen,
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Note that the pattern is brightest
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One of the more common ways of test
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3. . When the orange light passes f
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9. . Sound waves do not exhibit pol
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7. E Only concave mirrors and conve
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For people who believed that light
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What does this all mean? Time is re
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A spaceship flying toward the Earth
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Rutherford’s Gold Foil Experiment
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The Wave Theory of Electromagnetic
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The Problem with Rutherford’s Mod
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Don’t worry: you don’t need to
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A hydrogen atom is energized so tha
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where is the uncertainty in a parti
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electrons have mass, it is so negli
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chapters on mechanics are the resul
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You won’t need to calculate the n
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Photoelectro n Radius of Electron O
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5. . An electron is accelerated thr
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according to the formula , where l
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In radioactive substances, the numb
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A scale for measuring temperature,
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The points of maximum displacement
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Electromagnetic spectrum The spectr
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The amount of time it takes for one
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Given the period, T, and semimajor
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The substance that is displaced as
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A back-and-forth movement about an
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Refracted ray Refraction Restoring
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T Tail Tangent A body or set of bod
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Weber Weight The force involved in
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pinpointing what you need to study
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If you got a question wrong because
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