Foundations of Scientific Inquiry
Foundations of Scientific Inquiry
This domain tests how physics knowledge is built and checked: measurement, uncertainty, experimental design, data analysis, and safe use of apparatus. Expect items on SI units, significant figures, graphing, and distinguishing random from systematic error.
Core rules and concepts
- SI base units include meter, kilogram, second, ampere, kelvin, mole, and candela. Derived units such as newton (kg·m/s²) and joule (N·m) must stay consistent.
- Accuracy is closeness to an accepted value; precision is repeatability. Random error scatters repeated readings and averages down; systematic error shifts all readings and is not removed by averaging.
- Report results with significant figures matching the least precise measurement. In multiplication or division, keep the fewest significant figures; in addition or subtraction, keep the fewest decimal places.
- Dimensional analysis catches impossible equations: both sides must have the same units.
- On a linear graph, slope carries the physical meaning. Linearize nonlinear data, such as T² versus L for a pendulum, before extracting a constant.
Worked example
A pendulum of length 0.850 m completes 20 oscillations in 35.2 s. The period is T = 35.2/20 = 1.76 s. Using T = 2π√(L/g), solve g = 4π²L/T² = 4π²(0.850)/(1.76)² ≈ 10.8 m/s². Percent error from 9.81 m/s² is |10.8 − 9.81|/9.81 × 100 ≈ 10%. Length and timing uncertainties, plus reaction time, plausibly explain the high result.
Traps that cost marks
- Counting 20 oscillations as 20 periods when timing should begin and end at the same phase; miscounting adds a full period.
- Quoting calculator digits instead of applying significant-figure rules.
- Calling a consistently high reading random error; it is systematic.
- Forgetting to convert centimeters to meters or grams to kilograms before substituting.