科技英语.docx

1、科技英语Chapter 1Measurement1-1 Measuring things1. Physics is based on measurement.2. A physical quantity is defined by setting up a standard and assigning a unit to it.3. Scientists around the word will agree that your definition is(1) sensible (2) practical (3) accessible(4) invariable (5) reproducibl

2、e (6) indestructible1-2 The International System of Units1. Metric system-SIFranch name: Systme Internationale dunits2. SEVEV fundamental (base basic) SI unitsP. Q.UNITABBREVIATIONlengthmetermmasskilogramkgtimesecondselectric currentampereAtemperaturekelvinKluminous intensitycandelacdamount of subst

3、ancemolemolThe supplementary unitsplane angleradianradsolid anglesteradiansr3. Scientific notation and SI prefixes1-3 Three Basic Standards1. LENGTHThe meter is the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second.2. TIMEOne second is the time occupi

4、ed by 9,192,631,770 vibrations of the light (of a specified wavelength) emitted by a cesium-133 atom.3. MASS(1) a platinum-iridium cylinder(2) a second mass standardIt is the carbon-12 atom which, by international agreement, has been assigned a mass of 12 unified atomic mass units (abbr. U).1-4 Chan

5、ging UnitsChain-link conversionsChapter 2motion in a straight line2-1 Motion1. Kinematics and dynamics2. ParticleEvery small part of the object (every atom say) moves in exactly the same way.2-2 Speed, velocity and acceleration1. Average speed ,velocity and acceleration2. Instantaneous speed, veloci

6、ty and acceleration3. Speed is a scalar and always positive; velocity and acceleration are vectors and can be positive or negative.2-3 Free falling objectsWhen a falling object is free of all restraint (no friction, air etc.), and falls under the influence of gravity alone, the object is in a state

7、of FREE FALL, which means falling in a vacuum, so that the friction resistance and buoyant effect of the air do not affect the motion.2-4 The structure of matterAll ordinary matter that we encounter is made of ATOMS which, in turn, are composed of electrons, protons, and neutrons. The atoms of a par

8、ticular chemical element all have a certain number (the ATOMIC NUMBER Z of the element) of protons in their nuclei. An atomic nucleus also has a certain number of neutrons (the NEUTRON NUMBER N), the sum of N and Z being the MASS NUMBER A. There are several possible mass numbers for each chemical el

9、ements, each one designating an ISOTOPE of the element.Chapter 3vectors3-1 Vectors and scalars1. A vector is a quantity that has MAGNITUDE and DIRECTION and that follows certain rules of combination (translation property).2. A scalar is a quantity that has ONLY MAGNITUDE, requires NO specification o

10、f direction, and follows the rules of algebra.3-2 Unit vector1. Featuresunity magnitude, no dimensions, no units2. The only purpose to introduce a unit vector is to specify a DIRECTION.3-3 Multiplying vectors1. Multiplying a vector a by a scalar cScalar times vector2. The scalar product - dot produc

11、t is a scalar3. The vector product cross product is a vectorRight-hand Rule3-4 Vectors and physical lawsAny physical situation involving vectors can be described using several possible coordinate systems (reference frames). We usually choose the one of these that simplifies our work. However, the re

12、lation between the vector quantities does not depend on our choice. The laws of physics, written in vector form, use such relations. We say that the laws of physics are independent of our choice of reference frame.Chapter 4motion in a plane4-1 Three dimensional coordinate systemIn three dimensions,

13、a particle can be located by a VECTOR r, extending from the origin of coordinate system to the particle position.4-2 Projectile motion under no-atmosphere conditionswe analyze projectile motion (or any other motion for which acceleration is a constant) by resolving position r, velocity v and acceler

14、ation a into x and y components, treating each component as an independent, one-dimensional motion. 4-3 Uniform circular motionIn uniform circular motion, a particle moves with constant speed v in a circle of radius r. This is accelerated motion because the direction of the velocity is continuously

15、changing. The acceleration is always directed toward the center of the circle and has a constant magnitude.4-4 Relative motionThe position of P as measured by A is equal to the position of P as measured by B plus the position of B as measured by A.The velocity of P as measured by A is equal to the v

16、elocity of P as measured by B plus the velocity of B as measured by A.Both observers, in reference A and B, will measure the same acceleration for the moving particle.Chapter 5force and motion-I5-1 Limitations to Newtonian mechanicsThere are some important problems to which Newtonian mechanics does

17、not give correct answers. If the speeds of the particle involved are an appreciable fraction of the speed of light. We must replace Newtonian mechanics by Einsteins special theory of relativity. For problems on the scale of atomic structure (for example, the motions of electrons within atoms), we mu

18、st replace Newtonian mechanics by quantum mechanics. We now view Newtons mechanics as a special case of these two, more comprehensive theories. It is a very important special case, however, encompassing as it does the motions of objects that range in size from molecules to galaxies. Within this broa

19、d range it is highly accurate, as the successful maneuvering of space probes reminds us.5-2 Newtons laws1. Newtons first law (the law of inertia)Consider a body on which no net force acts. If the body is at rest, it will remain at rest. If the body is moving with a constant velocity, it will continu

20、e to do so.If the net force acting on a body is zero, it is possible to find a set of reference frames (inertia reference frames, in which the laws of Newtons mechanics holds) in which that body has no acceleration.Things at rest tend to stay at rest; things moving tend to continue moving. This tend

21、ency of things to resist changes in motion is INERTIA.2. Newtons second lawThe acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object.3. Newtons third lawYou cannot touch

22、without being touched (action force and reaction force)Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.An action-reaction pair always acts on different bodies so that they cannot possibly cancel each other.5-3 Mass and weightMa

23、ss is the quantity (scalar) of matter in a material object.Mass is a measure of the inertia of a material object, The more matter, the more inertia.Weight is the force (vector) upon an object due to gravity.Mass is an intrinsic property of the body, and more fundamental than weight.Measuring instrum

24、entsThe equal-arm balance and spring scaleChapter 6force and motion-II6-1 FrictionThe force of friction includes kinetic and static friction forces.The kinetic frictional force (associated with motion) is usually less than the maximum value of the static frictional force, which acts when there is no

25、 motion.The frictional force is basically an electro-magnetic force.6-2 Uniform circular motionA centripetal force is not a new kind of force.6-3 The forces of nature1. The gravitational force, 2. The electromagnetic force, 3. The weak force, 4. The strong force.Chapter 7work and kinetic energy7-1 A

26、 walk around Newtonian mechanicsNewtonian mechanics, grand as its structure may be, does fail when we apply it to particles moving at speeds comparable to the speed of light, yielding there to Einsteins special theory of relativity. It also fails when we apply it to motions of electrons in atoms, yi

27、elding in that case to quantum physics. The law of conservation of energy, however, holds in all these domains. It is a peak even higher then the peak of Newtonian mechanics.7-2 Work3. Motion in one-dimension with a constant forceWork is a scalar.Unit: Newtonmeter Nm; Joule Jelectron-volt eV; kilowa

28、tthour kWh4. Motion in one-dimension with a variable forcethe integral of the function F(x) between the limits xi and xf5. Work done by a springHookes law: To a good approximation for many springs, the force F(x) exerted by the spring is proportional to x, the extension of the spring.The work done b

29、y the spring on the agent that is stretching or compressing it is. The work done on the spring by that external agent is the negative of this quantity.derivatives and integrals; slope and areas7-3 Work-energy theoremThe change in the energy of a particle is equal to the total work done on that parti

30、cle by all the forces that act on it (net force).7-4 Powerunit: watt7-5 Reference frameThe principle of invariance: The laws of physics must have the same form in all inertial reference frames.Chapter 8the conservation of energy8-1 Conservation lawsConsider a system of particles, completely isolated

31、 from outside influences. As the particles move about and interact with each other, there is a certain property of the system does not change.8-2 Potential energyPotential energy (configuration energy) is energy “stored” in a system because work has been done against some conservative force. The ene

32、rgy stored in a stretched spring and the energy stored in an elevated mass are common examples.8-3 Conservative and nonconservative forcesA force is conservative if the work it does on a particle that moves through a round trip is zero; otherwise, the force is nonconservative.A force is conservative if the wo