Chapter 1 Physics Intro PDF

Chapter 1 : Introduction the Nature of science Physics Mrs. Pooja Brahmaiahchari What is PHYSICS??? The most basic science. The foundation of other sciences. Study of Matter and Energy and how they interact. The word physics comes from Greek, meaning nature or Knowledge of n...

Chapter 1 : Introduction the Nature of science Physics Mrs. Pooja Brahmaiahchari What is PHYSICS??? The most basic science. The foundation of other sciences. Study of Matter and Energy and how they interact. The word physics comes from Greek, meaning nature or Knowledge of nature. What? Why? How? When?  Physics is the foundation of many important disciplines and contributes directly to others. Chemistry, for example—since it deals with the interactions of atoms and molecules—is rooted in atomic and molecular physics. In architecture, physics is at the heart of structural stability, and is involved in the acoustics, heating, lighting, and cooling of buildings. Parts of geology rely heavily on physics, such as radioactive dating of rocks, earthquake analysis, and heat transfer in the Earth.  Most branches of engineering are applied physics. Physics has many applications in the biological sciences. Physics is involved in medical diagnostics, such as x-rays, magnetic resonance imaging (MRI), and ultrasonic blood flow measurements. Medical therapy sometimes directly involves physics; for example, cancer radiotherapy uses ionizing radiation. Physics can also explain sensory phenomena like how eye detect color, laser transmission. Model, theories and Laws Model Theory Laws A model is a simplified A theory is an explanation for A law uses concise language representation of complex patterns in nature that is to describe a generalized phenomena. supported by scientific evidence pattern in nature that is and verified multiple times by supported by scientific various groups of researchers. evidence and repeated experiments. Ex: planetary model of the Ex : Newton’s theory of gravity, Ex: Newton’s second law of atom motion Theory explains an entire group A law describes a single action of related phenomena Table 1.1 : Model, theory and law differences Scientific Method The scientific method is a process by which we ask questions about the world around us and hopefully can find answers. This method applies to ALL of the laws and principles which we will learn this semester. 1. Observe a phenomenon. 2. Form a hypothesis attempting to explain the phenomenon. 3. Test the hypothesis by a variation of the original experiment or observation. 4. Analyze results. 5. If results are consistent with hypothesis, then continue testing from step 3. 6. Else, form a new hypothesis accounting for the results and continue at 2. Physics Mechanics Kinematics (motion) Statics, Dynamics (forces) Electricity Magnetism Waves Optics (geometric optics) Nuclear Physics (Modern Physics) Aristotle (Greek 4th Century BC) The Greek philosopher Aristotle (384–322 B.C.) wrote on a broad range of topics including physics, animals, the soul, politics, and poetry. Galileo Galielie Father of the scientific method (along with the Englishman Francis Bacon 1500’s). Laid the foundation of modern experimentation and made contributions in physics, mathematics and astronomy. Sir Issac Newton Issac Newton was an English mathematician, physicist, astronomer, (1642-1727) related force and motion and studied light. Albert Einstien Albert Einstein (1879-1955) Photoelectric effect (Light is quantized) (Nobel Prize) Related mass and energy E=mc2  Physical quantities and units Physical quantity either by specifying how it is measured or by stating how it is calculated from other measurements. Measurements of physical quantities are expressed in terms of units, which are standardized values. SI units: Fundamental units and Derived units Length Mass Time Elecric Current Meter(m) Kilogram(kg) Second(s) Ampere(A) Table 1.2 Fundamental SI units Remember: Only these units are allowed in physics formulas! It is your responsibility to convert all quantities into basic units! Converting Units Sometimes we need to convert from one set of units into another. For example, my height is 1.80 m. a) What is this in inches? b) In feet? 1 inch = 0.0254 meters 1 meter = 3.281 feet Derived units All other physical quantities, such as force and electric charge, can be expressed as algebraic combinations of length, mass, time, and current (for example, speed is length divided by time); these units are called derived units. Metric Prefixes Prefixes correspond to powers of 10. Each prefix has a specific name. Each prefix has a specific abbreviation.  Accuracy, Precision Accuracy refers to how closely a measured value agrees with the correct value. The precision refers to how closely the individual measurements agree with each other. Significant figures The number of digits used to express a measured or calculated quantity. Digits that are Significant Non-zero digits are always significant. Any zeros between two non-zero digits are significant. A final zero or trailing zeros in the decimal portion ONLY are significant. For Example : How many significant figures are in: 1. 22.137 2. 0.00456 There are 5. All numbers are significant. There are 3. The zeros are simply placeholders and locate the decimal. They are not trailing zeros. They are not significant. For each of the following numbers, state the number of significant figures and the number of decimal places: a) 1.23 b) 0.123 c) 0.0123  Uncertainty is a quantitative measure of how much your measured values deviate from a standard or expected value. If your measurements are not very accurate or precise, then the uncertainty of your values will be very high. For example, A = 8.8 cm ±0.1 cm. The plus or minus amount is the uncertainty in your value. Percent Uncertainty One method of expressing uncertainty is as a percent of the measured value. If a measurement A is expressed with uncertainty 𝛿𝐴, the percent uncertainty (%unc) is defined to be 𝛿𝐴 %𝑢𝑛𝑐 = x 100% 𝐴 Approximation On many occasions, physicists, other scientists, and engineers need to make approximations or “guesstimates” for a particular quantity. Scientists often approximate the values of quantities to perform calculations and analyze systems. For Example :Approximate the Height of a Building in your campus. Problems 1. The speed limit on some interstate highways is roughly 100 km/h. (a) What is this in meters per second? (b) How many miles per hour is this? 2. An infant’s pulse rate is measured to be 130± 5 beats/min. What is the percent uncertainty in this measurement? 3. Do 0.00123 and 0.00028 have the same number of significant figures?