2 Learning Objectives List basic SI units and quantities they describe Convert measurements to scientific notationDistinguish between accuracy & precisionUse significant figures in measurements & calculations
3 Numbers as Measurements In science, numbers represent measurementsNumbers involve three thingsMagnitude how much?Dimensions length, mass, timeUnits of what?
4 The SI system The standard measurement system for science Base units Basic units that are not a combination of some other unitsDerived unitsAre combinations of base units
5 Base Units Physical Quantity (Dimension) Unit Abbreviation Mass KilogramkgLengthMetermTimeSecondsElectric currentAmpereATemperatureKelvinKLuminous intensityCandelacdAmount of substanceMolemol
6 Derived units Derived units are combinations of base units Base Unit m (length)m3 (volume)kg (mass)s (time)N (newton) for force1N = 1 kg∙ms2
8 Converting Prefixes & Units The main idea: multiply the given unit by a conversion factor yielding the desired unitConversion factor: a ratio of two units that is an equivalent to 1.Example: convert millimeters to meters1 mm x m = 1 x 10-3 m1 mmPractice 1A, #1-5
9 Converting units of area and units of volume How many cm2 are in 1 m2?How many cm3 are in 1 m3?How many in3 are in 1 L?
10 Scientific Method A way of thinking and problem solving A group of related processes and activities
11 Scientific Method: Important Terms Law vs. TheoryFact / ObservationHypothesisExperiment
12 Accuracy & Precision Accuracy Precision Nearness of a measurement to the true valuePrecisionDegree of exactness or refinement of a measurementRepeatability of a measurement
13 Precision describes the limit of exactness of a measuring instrument Significant figures reflect certainty of a measurementAre figures that are known because they are measured
14 Significant FiguresRepresent numbers known with certainty plus one final estimated digitReflect the precision of an instrument or measurementMust be reported properlyRequire special handling in calculations
15 Rules to determine significant digits 1. All non-zeros ARE2. All zeros between non-zeros ARE3. Zeros in front of non-zeros ARE NOT4. Final zeros to right of decimal AREFinal zeros without a decimal ARE NOT
17 Rules of calculating with significant figures When adding & subtracting, final answer must have fewest decimal places present in the calculation.When multiplying & dividing, final answer must have fewest significant digits present in the calculation.Number of figures in a constant are ignored wrt sig figs.
18 1.3 Language of PhysicsPhysical quantities often relate to one another in a mathematical wayData is collected in a table formData is graphedto show relationship of independent & dependent variablesWhen time is a variable it is usually the independent (x) variableManipulated & responding variables
19 Data Table and Graph Determining k through displacement x (m) Force (N)mass (kg)0.000.010.490.050.030.980.100.061.470.150.091.960.20
20 EquationsEquations indicate relationships of variables
21 Evaluating Physics Equations: Dimensional Analysis Can give you clues how to solve a problemCan help check many types of problems because…Dimensions can be treated as algebraic quantitiesExample: derive a formula for speedExample: How long would it take a car to travel 725 km at a speed of 88 km/h?
22 Order of Magnitude Estimates Physics often uses very large and very small numbersUsing powers of ten as estimates of the numbers can help estimate and check your answersExample: from the previous problem,