Physics.docx

***Physics 1*** **Introduction to Physics** - Physics is about the world and everything in it. - It can be thought of as humanity's attempts to describe and explain our universe. - It can be thought of as humanity's attempts to describe and explain our universe. **Physics**- A bod...

***Physics 1*** **Introduction to Physics** - Physics is about the world and everything in it. - It can be thought of as humanity's attempts to describe and explain our universe. - It can be thought of as humanity's attempts to describe and explain our universe. **Physics**- A body of knowledge which deals with the study of [matter, energy, and energy transformation.] **Matter**- Anything that occupies space and has mass. Things that can been seen or not. **Mass**- The amount of matter or molecules in a body **Weight**- The measure of gravitational pull on an object or body. **Energy**- The ability or capacity to do work. - **Einstein** related matter & energy not only in mathematical process but also by converting matter to energy and energy to matter. **E = mc^2^** (E- Energy; m- mass; c- speed of light) **Annihilation of matter**- converting **[matter to energy]** **Materializing of energy**- converting **[energy to matter]** **[Energy Transformation ]** "trans"- change "formation"- in form *Some forms of energy:* - Mechanical energy - Electrical energy - Light energy - Heat energy - Sound energy - Nuclear energy **Types of energy:** **Potential Energy** -- energy possessed by the body by virtue of its position. (P.E. = WH or P.E. = mgH) - W -- weight; H -- height; m = mass; g -- gravitational acceleration) **Kinetic Energy** -- energy possessed by the body by virtue of its motion. (K.E. = ½ mv2) - m -- mass; v -- velocity **[Main Branches:]** **Mechanics** -- deals primarily with the motion of bodies, the concept of force & its effect on the motion & shape of bodies (and with the properties of solids, liquids, & gas). **Sound & Wave Motion** -- deals with the transfer of energy by means of periodic disturbances through various media. **Heat** -- deals with thermal expansion, heat capacities of substances, changes of state, & heat transfer. **Thermodynamics** -- concerned with the relationship between heat and work. **Electricity & Magnetism** -- deals with the concept of the electric charge, the flow of electric charges, the concept of electric & magnetic fields & their interaction. **Optics** -- concerned with the fundamental concepts of electromagnetic waves, absorption & transmission of light, & the phenomena of reflection, refraction, interference, diffraction, & polarization. **Modern Physics** -- deals with the structure of the atom & the nucleus, & related phenomena like radioactivity, X-rays, nuclear fission & fusion. Also includes the study of fundamental particles, lasers & chain reactions. ***Scientific Method*** 1. Logical or orderly thinking 2. Observing 3. Experimenting 4. Expressing relationship among variables in equation form **Lesson 1: Measurement & Physical Quantities** **Systems of Measurement** The **English** or **British system** comprises units such as: - pound for force - yard for length - ounce for volume **SI system** The **metric system** constitutes units based on powers of 10, which makes it the preferred system to used in science. - For example: 1 kilometer (km) is equal to 103 meters (m), and 1 milligram (mg) is equal to 10--3 gram (gm). **[Two methods of measurement:]** 1. **Direct Method of Measurement** - Example: measuring the edge of the table -- compare it with some given standard - A ruler is placed along the edge of the table, & the number of times the whole edge is covered by the ruler is determined. - The length of the table = how many times that of the length of the ruler. (The length of the ruler has been used as a standard for comparison.) 2. **Indirect Method of Measurement** - Example: area of the table - The lengths of two of its adjoining edges are measured indirectly. - The area is obtained from the product of the two lengths. - Note: The area is not compared with any standard area; a computation is made from quantities which have been measured directly. A = L x W **Measurement-** is the process of comparing an unknown quantity with a known quantity or with a standard **Physical Quantities** I. **[According to Origin]** A. **Fundamental Quantities** - simplest types of quantities & cannot be reduced further 1. **Length** -- any dimension (length, width, height, arc of a circle, altitude, base, radius, diameter, distance) being measured using linear units (cm, m, in, ft., km, miles, yard, mm) 2. **Mass** -- amount of molecules or particles in a body 3. **Time** -- lapse of one event to another event; duration B. **Derived Quantities** -- quantities that are taken or formulated from two or more fundamental quantities Example: Area = LW; V = LWH; d = m/V; speed = d/t II. **[According to Specification]** A. **Scalar quantity** -- has magnitude and appropriate unit Example: speed = 60 km/hr. B. **Vector quantity** -- has magnitude, appropriate unit and direction Example: velocity = 60 km/hr. to the East **Fundamental Quantities & SI Base Units** **QUANTITY** **UNIT** **SYMBOL** --------------------- ---------- ------------ Length Meter m Mass Kilogram kg Time Second s Temperature Kelvin K Electric Current Ampere A Amount of Substance Mole mol Luminous Intensity Candela cd **Unit** -- is a value or quantity in terms of which other values or quantities are expressed. **Fundamental Units of Mass & Force Based System** +-------------+-------------+-------------+-------------+-------------+ | **System** | **Length | **Mass | **Force | **Time | | | Units** | Units** | Units** | Units** | +=============+=============+=============+=============+=============+ | Metric | Centimeter | Gram (g) | Dyne | Second (s) | | | (cm) | | | | | CGS | | Kilogram | Newton (N) | Second (s) | | | Meter (m) | (kg) | | | | MKS | | | | | +-------------+-------------+-------------+-------------+-------------+ | English | Foot (ft) | Slug | Pound (lb) | Second (s) | | | | | | | | FPS | | | | | +-------------+-------------+-------------+-------------+-------------+ **Unit Prefixes** - A **prefix** is a letter or a group of letters added at the beginning of the base word to change its meaning. - In measurement, a unit prefix or metric prefix can be used to make a new unit larger or smaller than the base unit. **Power of Ten** **Prefix** **Abbreviation** **Power of Ten** **Prefix** **Abbreviation** ------------------ ------------ ------------------ -- ------------------ ------------ ------------------ 10^12^ tera T 10^--2^ centi c 10^9^ giga G 10^--3^ milli m 10^6^ mega M 10^--6^ micro μ 10^3^ kilo k 10^--9^ nano n Example: - The wavelength of the green emission line in the spectrum of hydrogen is approximately 486 nanometers (nm). Express this length in meters. - Solution: n is the abbreviation of nano (10^--9^) 486nm = 486 x 10^--9^ m ***Dimensional Analysis*** - **[Dimensional analysis]** is a practical way of checking mathematical equations by finding out whether they are consistent in terms of their dimensions. - The dimensions of a given quantity can be reduced to a combination of the fundamental dimensions. - As mentioned earlier there are three basic or fundamental quantities. These 3 quantities are: Quantity SI Unit ------------ --------------- Length (L) m (meter) Mass (M) kg (kilogram) Time (T) s (second) - Dimension of a physical quantity shows how a derived quantity is related to the fundamental quantities of length, mass and time. - \[ \] -- the brackets denote the dimension of a physical quantity. \[length\] = L \[mass\] = M \[time\] = T Examples: Relate the following derived quantities to the 3 basic or fundamental quantities (length, mass, time). 1. Area = Length x Width \[Area\]= \[Length\] x \[Length\] = L x L = L2 2. Velocity -- change of displacement 3. Volume = length x width x height \[Volume\] = \[length\] x \[length\] x \[length\] = L x L x L = L3 Many problems in physics require the conversion of one unit of measurement to another. - **Unit Equality or conversion factor** is an equation that shows the equivalent amounts of different units. **Unit** **Equivalent Unit** **Unit** **Equivalent Unit** **Unit** **Equivalent Unit** --------------- --------------------- -- ------------ --------------------- -- ------------ ----------------------- **1 inch** **2.54 cm** **1 atm** **101325 Pa** **1 slug** **14.59 kg** **1 gal** **3.788 L** **1 foot** **12 inches** **1 N** **0.2248 lb** **1 calorie** **4.186 J** **1 mile** **5280 ft** **1 eV** **1.602 x 10^-19^ J** Examples: 1. Problem: How many inches are there in 12 m? Solution: From the given table there is no direct conversion from inches to meters. Relate inches to centimeters by first converting the metric quantities. 1 in = 2.54 cm; 100 cm = 1 m Using d as the variable to represent the length of 12 m and the appropriate conversion factors, the solution for the problem is as follows. - There are 472 in for every 12 m. 2. MPIWI uses cubic meter (m^3^) as the unit of a volume of water used in each household. Determine how many cubic meters are there in20-L tank of water. Solution: Let the volume of the tank be represented by V. The unit equalities that can be used are the following: 1L = 1,000 mL; 1 mL = 1 cm^3^; 100 cm = 1m Setting the equation: - There are 0.02 m^3^ in a 20 L tank of water. Note: 100 cm^3^ is not equal to 1 m^3^. 3. The speed of a car as measured by a speedometer is 90 kilometers per hour (km/hr). Convert this unit to centimeter per second (cm/s) Solution: For this case, the unit is expressed in a ratio, convert units used in both the numerator and the denominator. Let v represent the speed of the car. The following unit equalities are: 1 km = 1,000 m; 1 m = 100 cm; 1 hr = 3,600 s The equation is: **Some conversion factors for length and mass:** **UNIT** **EQUIVALENT UNIT** --------------------- ------- ------------------------ **1 centimeter** **=** **0.3937 inches (in)** **1 inch** **=** **2.54 centimeters** **1 meter** **=** **39.37 inches** **1 meter** **=** **3.28 feet (ft)** **1 mile** **=** **5280 feet** **1 mile** **=** **1.609 kilometers** **1 kilogram** **=** **2.205 pounds (lb)** **1 pound** **=** **453.6 grams** **1 ton (metric)** **=** **2205 pounds** **1 ton (British)** **=** **2000 pounds** **1 pound** **=** **16 ounces (0z)** **[Scientific Notation]** - A "short cut" to writing extremely large or small numbers by expressing them as a number between 1 & 10 multiplied by a power of 10. - Example: - Velocity of light = 30,000,000,000 cm/s - Mass of electron = 0.000000000000000000000000000000911 kg - Avogadro's number = 602,000,000,000,000,000,000,000 molecules/mole **[Lesson 1.1: Measurement]** ***Limitations of Measurement*** [Two kinds of certainty (or uncertainty) in scientific measurement:] - **Accuracy** -- **[exactness]** of the measurement - **Precision** -- involves the **[repeatability]** of a measurement ***Accuracy in Measurement:*** - Concerns how closely a measurement or series of measurements reflects the actual value. - If the set of measurements is close to the true or accepted value. - The more exact the measurement is, the more accurate it is. ***Precision in Measurement:*** - How close several measurements are to each other. - The values are close to one another. ***[Systematic Errors and Random Errors]*** **Error-** is the technical term for uncertainty in reading a measurement. - An error in measurement means an uncertainty between the measured value and the standard value. - Our reading may be too small or too large. - We make a positive error if our reading is too large and a negative error if our reading is too small. ***Two Classes of Error*** 1. **Systematic error** - When the error produced is always of the same sign. - It is committed if the measurement tends to make all observations too big or too small. **[Classified into three:]** - **Instrumental errors** -- errors caused by faulty or inaccurate apparatus. - **Personal** -- errors that involve some peculiarity or bias of the observer, like the tendency to assume that the first reading is correct. This is also committed due to eye strain, fatigues, or position of the eye in reading the scale. - **External** -- errors that are caused by external conditions like temperature, humidity, wind, and vibrations. 2. **Random error** - When positive and negative errors are equally probable to occur. - These errors are erratic errors that are variations due to a lot of factors, each of which adds or contributes to the total error. - These factors vary and are unknown, therefore, the error produced is a matter of chance which means that the probability of making both positive and negative errors are equal. - Taking a large number of observations will lessen the effect of error in the experiment because they are subject to the laws of chance. **Estimating Errors from Multiple Measurements of a Physical Quantity Using Variance** - How to estimate errors from multiple measurements of a physical quantity using variance? - Have several readings, n readings, take the sum of these readings and take the arithmetic mean. - Then, take the individual deviation, d, of the readings from the arithmetic mean. - Take the average of these deviations by getting the sum of the deviations (without regard of sign) divided by the number of observations, n. **Direct Proportion:** "If one quantity increases, the other quantity increases at the same rate. If one quantity decreases, the other quantity decreases at the same rate." **Inverse Proportion:** "If one quantity increases, the other quantity decreases at the same rate. If one quantity decreases, the other quantity increases at the same rate."