Physics Paper 1

• Absolute Uncertainties


  The interval that a value is said to lie within, with a given level of confidence
• Accuracy


  A measure of how close a measurement is to the true value
• Analogue Apparatus


  Measuring apparatus such as rulers, beakers and thermometers that rely on the experimenter reading off a scale to determine the measurement
• Anomalies


  Data points that don't fit the pattern of the data. You should determine why an anomalous result has occurred before removing it. Repeat readings help remove anomalies
• Control Variables


  Variables that must remain the same throughout an experiment so as to not affect the results
• Dependent Variables


  The variable being measured in an experiment. It is dependent on the independent variable. The dependent variable should be plotted on the y-axis of a graph

  
• Digital Apparatus


  Measuring apparatus such as ammeters, voltmeters and digital calipers that digitally measure and display a measurement
• Fiducial Marker


  A thin marker, such as a splint, that is used to ensure readings are taken from the same place each time. They are used to improve the accuracy of measurements
• Gradient


  The change in the y-axis value over the change in the x-axis value between two points. If the graph is curved, a tangent can be drawn to calculate the gradient at a specific point

  
• Independent Variables


  The variable that is changed by the experimenter in an experiment. The independent variable should be plotted on the x-axis of a graph
• Line of Best Fit


  A line drawn on a graph to demonstrate the pattern in the plotted data points
• Percentage Uncertainties


  The uncertainty of a measurement, expressed as a percentage of the recorded value
• Precision


  A measure of how close a measurement is to the mean value. It only gives an indication of the magnitude of random errors, not how close data is to the true value
• Prefixes


  Added to the front of units to represent a power of ten change
• Random Errors


  Unpredictable variation between measurements that leads to a spread of values about the true value. Random error can be reduced by taking repeat measurements
• Repeatable


  The same experimenter can repeat a measurement using the same method and equipment and obtain the same value
• Reproducible


  An experiment can be repeated by a different experimenter using a different method and different apparatus, and still obtain the same results
• Resolution


  The smallest change in a quantity that causes a visible change in the reading that a measuring instrument records
• Resolution of Forces


  The splitting of a force into its horizontal and vertical components
• Scalar Quantities


  A quantity that only has a magnitude, without an associated direction. Examples include speed, distance and temperature
• SI Units


  The standard units used in equations. They are: metres, kilograms, seconds, amps, Kelvin and moles
• Significant Figures


  A measure of a measurement's resolution. All numbers except zero are counted as a significant figure. When zeros are found immediately after a decimal place, they too are counted
• Systematic Errors


  Causes all readings to differ from the true value by a fixed amount. Systematic error cannot be corrected by repeat readings, instead a different technique or apparatus should be used
• Triangle of Forces


  A method of finding the resultant force of two forces. The two forces are joined tip to tail and the result is then the vector that completes the triangle

  
• Vector Quantities


  A quantity that has both a magnitude and an associated direction. Examples include velocity, displacement and acceleration
• Vernier Scales


  The type of scale used on calipers and micrometers, that involve reading from a fixed scale and a moving scale to produce accurate measurements
• Zero Errors


  A form of systematic error, caused when a measuring instrument doesn't read zero at a value of zero. This results in all measurements being offset by a fixed amount
• Anomaly


  A data point or a value in a set of results that does not fit the trend of the data and is therefore an unexpected result
• Systematic error


  An error that occurs due to faults in equipment or experimental method. Systematic errors cause the result to differ by the same amount each time, making them predictable. They can occur due to not calibrating an instrument correctly.
• Random errors


  • They cause fluctuations in readings that affect precision and cannot be removed
• Reducing random errors


  1. Take at least three repeats and calculate a mean

  2. Use computers/data loggers

  3. Use higher resolution equipment
• The mass balance reads 1004 g when a 1kg mass is placed on it. This is a systematic error.
• Systematic error reduction


  Calibrate apparatus before using e.g. zero the balance when it is empty
• Electronic noise in the circuit of an ammeter is a random error
• Measuring background radiation before measuring the radioactivity of a source


  Reduces systematic error by accounting for background radiation
• Precision


  How consistent/close together repeat readings are - the closer they are, the more precise they are
• Repeatability


  If the original experimenter can redo the experiment with the same equipment and method then get the same results, the experiment is repeatable
• Reproducibility


  If the experiment can be redone by a different person or with different techniques and equipment and the same results are found, it is reproducible
• Resolution


  The smallest change in the quantity being measured that gives a recognisable change in reading
• Absolute uncertainty


  Uncertainty given as a fixed quantity