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PHYSICS Introduction
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What is Science - systematic knowledge of the physical or material world gained through observation and experimentation.
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What is Physics? - the science that deals with matter, energy, motion, and force.force - The Rules of Nature.
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Hypotheses – tentative and testable statements that must be capable of being supported or not supported by observational evidence. To be accepted as a good hypothesis, there must exist a test or experiment to try and prove it wrong. Theory - based on natural and physical phenomena and are capable of being tested by multiple independent researchers. Unlike hypotheses, scientific theories are well- established and highly- reliable explanations, but may be subject to change as new areas of science and new technologies are developed
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Independent variable – factor that is adjusted by the experimenter to see what effect the change has on the dependent variable Dependent variable – factor whose value changes because of a change in the independent variable
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Inference – a reasonable conclusion or possible hypotheses based on observations Observation - A conclusion or data gathered, based upon directly observing something. - Observations can be made with eyes, ears, nose, or touch.
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Distance The entire linear distance traveled despite side trips Displacement The distance between points “A” and “B”. “As the crow flies” From A to B = 250 m From A to B = 40 m Point A Point B Point A Point B
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LAWS-describe the relationships between various phenomena
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Boyle’s Law Charles’ Law Cole’s Law
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Scientific Law- expressed by words Laws in physics- expressed by math equations
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THEORY- reasonable explanation of observed events that are related.
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Theories often involve models. e.g. Atomic Theory Democritus’ Model Thomson’s Model Rutherford’s Model Bohr’s Model Electron Cloud Model
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Experiments test theories.
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Physical Science the study of the physical universe.
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The two main branches are physics and chemistry.
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These two overlap; the main difference is that physics always deals with the concept of energy.
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The major areas within Physics are: mechanics, thermodynamics, waves, optics, electricity and magnetism, relativity, and nuclear physics.
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Scientific Method Five Steps State Problem Research it Hypothesis - extends thinking beyond known facts Experiment Draw Conclusions
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Certainty in science One should always question the validity of scientific Laws, Theories, or Hypotheses.
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METRIC SYSTEM - uses a decimal basis for multiples and fractions of the basic units of measure.
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International System of Units = The SI system
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Units of measure are used to describe physical quantities. e.g. the meter is the unit of length
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Seven fundamental units of measure: 1. length meter 2. masskilogram 3. timesecond 4. electric currentampere 5. temperaturekelvin 6. amount of substancemole 7. luminous intensitycandela
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Combinations of these units are used to measure other physical quantities. (e.g. mass density) These are called derived units.
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METER Standard meter was a metal bar until 1960. Now 1 meter = the distance light travels in a vacuum in 1/299 729 458th of a second.
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FORCE AND WEIGHT Newton is the accepted unit. Force needed to accelerate a one kilogram mass by one m/s 2.
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THE SECOND one second = 9 192 631 770 vibrations of cesium-133 atoms.
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1 ml H 2 O = 1 cm 3 H 2 O = 1 g H 2 O or… 1 ml = 1 cm 3 = 1g heat required to change temp of 1 g liquid of H 2 O 1° centigrade (Kelvin) is 1 calorie
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ACCURACY - the closeness of a measurement to the accepted value for a specific physical quantity.
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absolute error- actual difference between the accepted value and the measured value.
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E a = (O – A), where Ea is the absolute error, O is the observed value, and A is the accepted value.
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Relative Error - expressed as a percentage. (often called percentage error)
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E r = (E a / A) x 100% where E r is the relative error, E a is the absolute error, and A is the accepted value.
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PRECISION - the agreement among several measurements that have been made in the same way.
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Precision is expressed in terms of DEVIATION.
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Absolute deviation- difference between a single measured value and the average of several measurements made in the same way.
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Relative Deviation- the percentage average deviation of a set of measurements.
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Is this Accurate, Precise, Both, or Neither
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SCIENTIFIC NOTATION M 10n M is a number greater than or equal to 1, but less than 10. n is the number of places the decimal point has been shifted. Moved left, n is pos. Moved right, n is neg.
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Order of magnitude. numerical approximation to the nearest power of ten.
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DATA, EQUATIONS, GRAPHS, DIMENSIONAL ANALYSIS.
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Scalar quantities. quantities expressed by single numbers with appropriate units. Vector quantities. Quantities that require magnitude and direction. Usually depicted by arrows.
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Two vectors that act on the same point are called components.
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RULES OF PROBLEM SOLVING
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1. Carefully find what is being asked. Write down all given data.
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2. Write down all the symbols and units for the quantities called for.
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3. Write down the basic equation relating the known and unknown quantities.
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4. Solve for the unknown quantity to find the working equation.
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5. Substitute the given data into the working equation.
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6. Perform the mathematical operations with the units alone. Unit analysis Dimensional analysis
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7. Perform the math
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8. Check the answer for reasonableness
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9. Review the entire solution.
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