Chapter 1 The Science of Physics

Topics of physics The atom and its partsBehavior of submicroscopic particles Quantum mechanics Particle collisions, particle accelerators, nuclear energy Particles moving at any speed, including very high speeds Relativity Electrical charge, circuitry, permanent magnets... Electricity, magnetism, and light Electromagnetism Mirrors, lenses, color, astronomy LightOptics Springs, pendulums, soundSpecific types of repetitive motions Vibrations and wave phenomena Melting and freezing processes, engines... Heat and temperatureThermodynamics Falling objects, friction, weight, spinning objects Motion and its causesMechanics ExamplesSubjectsName Areas within Physics

The scientific Method Make observations And collect data that Lead to a question Formulate Hypothesis Test Hypothesis: Experiments Interpret Results, and revise the hypothesis if necessary State Conclusions in a form that can be evaluated by others SCIENTIFICALLY PROVEN X

Physics uses models Models describe only a part of reality E.g. Basketball - fig 1.4 System: what you are studying. E.g. in the basketball example you are studying the ball and its motion Other factors such as color, size, spin, aren’t considered

Galileo’s Hypothesis What was the Question? What was his hypothesis? How can we test his hypothesis? Experiment

Section Review Name the areas of physics Identify the area of physics that is most relevant to each of the following situations. Explain your reasoning. –A high school football game –Food preparation for the prom –Playing in the school band –Lightning in a thunderstorm –Wearing a pair of sunglasses outside in the sun What are the activities involved in the scientific method? Give two examples of ways that physicists model the physical world. Identify the area of physics involved in each of the following tests of a lightweight metal allow proposed for use in sailboat hulls: –Testing the effects of a collision on the alloy –Testing the effects of extreme heat and cold on the alloy –Testing whether the alloy can affect a magnetic compass needle

Measurements in experiments Dimension: tells us what physical quantity we are dealing with. Three basic dimensions: –Length –Mass –Time Units: tells us how much of that physical quantity we are talking about

SI standards In 1960, an agreement was made on seven base units We will deal with only three Second (s)Time Kilogram (kg)Mass Meter (m)Length UnitDimension

Prefixes SI uses prefixes to accommodate extremes The distance between stars is approximately m The distance between atoms in a solid is approximately m Mr. Samuel can’t even say those numbers You shouldn’t be expected to say them either These numbers are expressed in powers of 10. The distance between stars is approximately 1 x The distance between atoms is 1 x m

Prefixes PowerPrefixAbbreviationPowerPrefixAbbreviation atto-a10 1 deka-da femto-f10 3 kilo-k pico-p10 6 mega-M nano-n10 9 giga-G micro-  tera-T milli-m10 15 peta-P centi-c10 18 exa-E deci-d

Converting Measurements Use conversion factor that will cancel with the units you are given to provide the units you need. The units to which you are converting should usually be in the numerator. It helps to cross out the units that cancel Lets PRACTICE

Practice 1A A human hair is approximately 50  m in diameter. Express this diameter in meters. A typical radio wave has a period of 1  s. Express this period in seconds A hydrogen atom has a diameter of about 10nm. –Express this diameter in meters. –Express this diameter in millimeters. –Express this diameter in micrometers. The distance between the sun and the Earth is about 1.5 x m. Express this distance with an SI prefix and in kilometers. The average mass of an automobile in the United States is about x 10 6 g. Express this mass in kilograms

Accuracy vs Precision Accuracy is the closeness of measurements to the correct or accepted value of the quantity measured. Precision is the closeness of a set of measurements of the same quantity made in the same way.

Accuracy vs Precision

Accuracy suggests that the experiment has accounted for all factors that might affect the system being studied Precision lets us know that the experiment was done carefully in a controlled environment