CAIE Physics A-level Notes - Topic 1: Physical Quantities and Units PDF

CAIE Physics A-level This work by [PMT Education] is licensed under [CC BY-NC-ND 4.0] ---------------------------------------------------------------------------------------- 1. **- Physical Quantities and Units** 1. - SI Units ========== **Un...

CAIE Physics A-level This work by [PMT Education] is licensed under [CC BY-NC-ND 4.0] ---------------------------------------------------------------------------------------- 1. **- Physical Quantities and Units** 1. - SI Units ========== **Unit** ------------------------------------ ---------- Mass Length Time Current Temperature Amount of substance (A-level only)  -- --- -- d n p -- --- -- - Errors and Uncertainties ========================== - Take **at least 3 repeats** and calculate a **mean**, this method also allows anomalies to be identified - Use **computers/data loggers/cameras** to reduce human error and enable smaller intervals - Use **appropriate equipment**, e.g a micrometer has higher resolution (0.1 mm) than a ruler (1 mm) - **Calibrate** apparatus by measuring a known value (e.g. weigh 1 kg on a mass balance), if the reading is inaccurate then the systematic error is easily identified - In radiation experiments correct for background radiation by measuring it beforehand and subtracting it from the final results - Read the meniscus (the central curve on the surface of a liquid) at eye level (to reduce parallax error) and use controls in experiments -------------- ---------------------------------------------------- **Accuracy** A measurement close to the true value is accurate. -------------- ---------------------------------------------------- - ### Adding / subtracting data - ADD ABSOLUTE UNCERTAINTIES - ### Multiplying / dividing data - ADD PERCENTAGE UNCERTAINTIES - ### Raising to a power - MULTIPLY PERCENTAGE UNCERTAINTY BY POWER = 6% % uncertainty in area = 6 x 2 (2 is the power from *r*^2^ ) = 12% - Scalars and Vectors ===================== ------------------------------------ ---------------------------------------------------- Distance, speed, mass, temperature Displacement, velocity, force/weight, acceleration ------------------------------------ ---------------------------------------------------- - ### Calculation 12^2^ + 5^2^ = 169 ------------------ - ### Scale drawing ### x = V cos θ y= V sin θ