* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Review for Spring Semester Final
Survey
Document related concepts
Second law of thermodynamics wikipedia , lookup
Thermodynamics wikipedia , lookup
Electric charge wikipedia , lookup
Electrical resistance and conductance wikipedia , lookup
Relative density wikipedia , lookup
Fundamental interaction wikipedia , lookup
Bernoulli's principle wikipedia , lookup
Electromagnetism wikipedia , lookup
Anti-gravity wikipedia , lookup
Electrostatics wikipedia , lookup
Lorentz force wikipedia , lookup
Thermal conduction wikipedia , lookup
Centripetal force wikipedia , lookup
Weightlessness wikipedia , lookup
Newton's laws of motion wikipedia , lookup
Transcript
Principle of Technology Review for Spring Semester Final 1.1 Forces in Mechanical Systems A force is a push or a pull. Force is a vector. It has both magnitude and direction. Its magnitude is measured in pounds or Newtons. Newton’s first law says that an object will remain at rest or will continue in a straight line unless it is acted on by a net force. Unbalance forces result in net force acting on an object. Balance forces result in no net force acting on an object. If two forces act on an object and the forces act in a straight line, the magnitude of the resultant is either the sum or the difference between the two forces magnitudes. If two forces on an object do not act in a straight line, the resultant can be found using the head-to-tail method of vector addition. The mass of an object is a measure of the object’s inertia. The weight is a measure of the force exerted on the object by gravity. A torque is exerted on a body when a force is applied and the line of action of the force does NOT pass through the body’s axis of rotation. The torque equals the force times the lever arm. If not net torque is exerted on a on a body, it will remain at rest or it will continue to rotate at a constant rate. 1.2 Pressure in Fluid Systems Matter can exist in fours states: solid, liquid, gas and plasma. Liquids and gases are called fluids. The density of a substance is its mass per unit volume. The density of water is 1 g/cm3. Weight density is weight per unit volume. Pressure is force divided by area over which the force acts. We treat pressure as a scalar. In SI units, pressure is measured in Pascals, where 1 Pa = 1 N/m2. Pressure increases with depth of a fluid. For a given fluid, the pressure does not depend on the size or shape of the container. When an object is submerged in a fluid, an upward force is exerted on the object caused by the pressure difference between the top and bottom of the object. The force is called buoyant force. The buoyant force exerted on an object equals the weight of the fluid displaced by the object. A pressure applied to a confined fluid is transmitted throughout the fluid. Atmospheric pressure is caused by the weight of the air above a given area. Atmospheric pressure can be measured with a barometer. Absolute pressure is the s um of the gage pressure and atmospheric pressure. 1.3 Voltage in Electrical Systems Newton’s law of universal gravitation and Coulomb’s law are both inverse square laws. The magnitude of both forces decreases with the square of the distance between the masses and the charges. Atoms are composed of protons, neutrons, and electrons. Protons are positively charged, electrons are negatively charged, and neutrons have no charge. The flow of electrons in an electrical system is a current. Unlike charges attract; like charges repel. An electric field is a model of the alteration of space around one or more charges. You can use the field to predict the force exerted on a charge placed in the field. The potential difference, or voltage, between two points in a uniform electric field is the product of the field strength and the distance between the points. Voltage is the prime mover in electrical systems. A battery is a source of DC voltage. It can maintain a current in an electrical circuit. Batteries or cells can be connected in series to increase voltage. 1.4 Temperature in Thermal Systems The thermal energy of a body is the total kinetic energy of motion all the particles that make up the body. The temperature of a body is determined by the average kinetic energy of the particles that make up the body. A thermometer measures the temperature in degrees Celsius or degrees Fahrenheit. Heat is energy that flows from one body to another because of a temperature difference. Whenever two bodies are brought together, heat flows from the body with the higher temperature to the body with the lower temperature. The amount of heat transferred to an object varies linearly with the object’s temperature change, as long as there is no change of state: Q = mTC. If heat is transferred to a substance and it changes state, its temperature does not change. 2.1 Work in Mechanical Systems Mechanical systems use force and torque to cause desired movement--and do useful work. Work is done when a force or torque moves an object. Work is done only while the force or torque is applied in the direction of movement. Work equals force times displacement or torque time the angle. Work is measured in ftlb or Nm (= J). (W = Fd; W = ) The displacement used to calculate work is the distance the object moves while the force is applied. Efficiency describes how well a machine performs work. Efficiency is the ratio of output worj to input work. (Eff = Wout/Win) Angle can be measured in either radians or degrees. The radian is a dimensionless unit and us used in most calculations involving angles. Other Units Quantity Force or Weight, F or W Torque, Work, W Density, Weight Density, w Pressure, P ftlb ftlb slugs/ft3 lb/ft3 lb/ft2 or psi (lb/in2) Charge, q Electric Field, E Electric Potential Difference, V Heat, Q Specific Heat, C - Heat of Formation, Hf Heat of Vaporization, Hv - cal/g, or J/g SI Prefixes Prefix kilo- (k-) hecta- (h-) deka- (da-) base unit deci- (d-) centi- (c-) milli- (m-) - Factor 1000 100 10 1 0.1 0.01 0.001 Exponent Form 103 102 101 100 10-1 10-2 10-3 Conceptual Equations Pythagorean Theorem c2 a2 b2 Trigonometry Functions sin opp hyp F ma Amount of Substance, n Luminous Intensity, Iv SI Unit Newton (N, or kgm/s2) Nm (Joule, J) Nm (Joule, J) g/cm3 N/m3 Pascal, Pa (= N/m2) Coulomb, C N/C Volt, V (Nm/C, or J/C) Nm (Joule, J) cal/goC, or J/goC cal/g, or J/g Force Base Units Quantity Length, l / Distance, d Mass, m Time, t Electric Current, I Temperature, T English pound (lb) English Unit foot (ft) slug second (s) degree Fahrenheit (oF) - SI Unit meter (m) kilogram (kg) second (s) ampere (A) Kelvin (K) Net Force mole (mol) Torque - candela (cd) Fnet F Weight W mg FL Density m V cos adj hyp tan opp adj Weight Density Work W F d W w V Pressure P F A Pressure in a Fluid P w h Buoyant Force Fbuoyant w Vobject weight of fluid displaced Pascal’s Principle (Formal for Hydraulic and Pneumatic Systems) Parea1 Parea2 or F1 F2 A1 A2 Absolute Pressure PAbsolute PGage PAtmospheric Newton’s Gravitational Law Fg G m1m2 d2 Coulomb’s Law FE K q1 q 2 d2 Electric Field F E E q Electric Potential, or Voltage, or Electric Potential Difference V Ed Converting Between Celsius and Fahrenheit Tc 5 TF 32 9 9 TF TC 32 5 Heat Transfer without Phase Change Q mTC Heat Transfer with Phase Change (Melting/Freezing) Q mH f Heat Transfer with Phase Change (Vaporization/Condensation) Q mH v Quantity Symbols Symbol Quantity a, b, c lengths of triangles sides (c = hypotenuse) F force m mass a acceleration W weight or work g acceleration due to gravity torque L length of lever arm density V volume weight density w P A h G d K q E V TC TF Q T C Hf Hv pressure area fluid depth universal gravitational constant distance Coulomb’s constant charge electric field electric potential (also called voltage) temperature in degrees Celsius temperature in degrees Fahrenheit heat transferred change in temperature specific heat heat of formation heat of vaporization Some Constants and Equivalent Measures g = 9.8 m/s2 -11 2 2 G = 6.67 x 10 Nm /kg K = 9.0 x 109 Nm2/C2 qelementary = 1.60 x 10-19 C 1 m = 3.28 ft 1 slug = 14.59 kg 1 lb = 4.45 N 1 cal = 4.184 J 1 Cal = 1000 cal 1 atm = 760 mmHg = 101.3 kPa