Measurements and their errors

• SI units: Mass (kg), Length (m), Time (s), Amount of substance (mol), Temperature (K), Electric current (A)
• Estimation is a skill physicists use to approximate the values of physical quantities.
• Estimation is used to make comparisons or check the reasonableness of calculated values.
• SI units of force: kgm/s^2 (also known as N)
• SI units of voltage: As kgm^2/s^2 (also known as J)
• Prefixes for SI units: Tera (T), Giga (G), Mega (M), Kilo (k), Centi (c), Milli (m), Micro (μ), Nano (n), Pico (p), Femto (f)
• Converting mega electron volts to joules: 1eV = 1.6x10^-19 J
• The uncertainty in the y-intercept can be found by calculating the difference between the best and worst y-intercepts
• The acceleration of the mass is 13 m/s^2 ± 0.8 m/s^2
• The uncertainty in the gradient can be found by calculating the difference between the best and worst gradients
• 100 m is two orders of magnitude greater than 1 m
• The approximate area of the entire atom is 1 x 10^-20 m (to the nearest order of magnitude)
• The diameter of nuclei has an order of magnitude of around 10^-14 m
• The percentage uncertainty in the area of the circle is 12% ± cm^2
• The difference in temperature is 25 K ± 1 K
• Converting kWh to joules: 1 kWh = 3.6x10^6 J
• Random errors affect precision and cannot be completely eliminated
• Systematic errors affect accuracy and can be reduced by calibrating apparatus and correcting for background radiation
• Resolution: The smallest change in the quantity being measured that gives a recognizable change in reading.
• Uncertainty in a reading: ± half the smallest division.
• Uncertainty in a measurement: At least ±1 smallest division.
• For repeated data: Uncertainty is half the range (largest - smallest value), shown as mean ± 2 range.
• Precision: Measurements that are consistent and fluctuate slightly about a mean value.
• Digital readings and given values: Uncertainty is either quoted or assumed to be ± the last significant digit.
• Uncertainty: The bounds in which the accurate value can be expected to lie.
• Meniscus: The central curve on the surface of a liquid.
• Reproducibility: The ability to redo an experiment by a different person or with different techniques and equipment and obtain the same results.
• Readings: When one value is found.
• Repeatability: The ability to redo an experiment with the same equipment and method and obtain the same results.
• Absolute Uncertainty: Uncertainty given as a fixed quantity.
• Measurements: When the difference between two readings is found.
• Combining uncertainties by adding/subtracting data: Add absolute uncertainties.
• Fractional Uncertainty: Uncertainty as a fraction of the measurement.
• Percentage Uncertainty: Uncertainty as a percentage of the measurement.
• Accuracy: A measurement close to the true value.