RNT1 Lecture Notes - Lecture 1: Scientific Method, Net Force, Caesium
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What is Physics?
Physics attempts to explain the universe and how it works by breaking it into its smallest
possible components and, given the interactions among them, deduce how the universe works at
For us for the time being: Physics is the study of motion.
How physics (and science) is done.
The Scientific Method.
1. Observation — Newton sees an apple fall
2. Hypothesis — A force called gravity pulled the apple to the Earth
3. Prediction — Same force of gravity holds the Moon in orbit about the Earth
4. Experiment — Measure the motion of the Moon
5. Conclusion — If the prediction and the result of the experiment disagree within experimental
uncertainty then the hypothesis is rejected. If the prediction and the experimental result agree
within the uncertainty, the hypothesis is supported.
The ultimate decision as to the validity of a scientific idea is how well it predicts the results of
Note: The scientific method as described above is an ideal. No single scientist or group of
scientists follow the method as described. However science follows the spirit of the scientific
method—no idea is accepted unless it is supported by experimental evidence.
International System of Units (SI)
Unit of Distance: meter
Originally: One ten-millionth of the distance from north pole to equator
Original Standard - platinum-iridium bar with two finely engraved lines one meter apart.
Current: the meter is defined so that the speed of light is