Chapter 1: The Science of Physics

Mr. DunkPre-AP Physics

Pearland High School

What is physics?

physics is the study of the physical world

physics is everywhere; any problem that deals with temperature, size, motion, position, shape, or color involves physics

Areas Within Physics

Name Subjects

mechanics motion and its causes

thermodynamics heat and temperature

vibrations and waves

specific types of repetitive motion

optics light

electromagnetism electricity, magnetism, and light

Areas Within Physics

Name Subjects

Relativity Particles moving at any speed, including very high speed

Quantum mechanics Behavior of submicroscopic atomic particles

What is physics?

scientific method – an organized process used to conduct scientific investigations or experiments; there is no single procedure, but the following general steps are always included:

The Scientific Method make observations and collect data

that lead to a question formulate and objectively test

hypothesis by experimentation interpret results and revise the

hypothesis and experiment if necessary

state conclusions in a form that can be evaluated by others

The Scientific Method

model – a replica or description designed to show the structure or workings of an object, system, or concept

system – a set of items or interactions considered a distinct physical entity for the purpose of study; usually, this involves a single object and the items that immediately affect it

The Scientific Method

using models can help to build hypotheses

a plan or model for investigation or experimentation

controlled experiment – an experiment involving the manipulation of a single variable or factor

Measurement in Experiments

SI Base Units of Measurements

unit symbol

length meter m

time second sec or s

mass kilogram kg

current ampere A

temperature kelvin K

Measurement in Experiments

SI Base Units of Measurements

unit symbol

luminous intensity

candela cd

amount of a substance

mole mol

all other units are called derived units because they are based on combinations of two or moreof the SI base units

Measurement in ExperimentsCommon Numerical Prefixes

10-18 atto- a 101 deka- da

10-15 femto-

f 103 kilo- k

10-12 pico- p 106 mega-

M

10-9 nano- n 109 giga- G

10-6 micro-

µ 1012 tera- T

10-3 milli- m 1015 peta- P

10-2 centi- c 1018 exa- E

10-1 deci- d

Measurement in Experiments

dimensional analysis is an important skill in physics since you will have to convert back and forth among various units

INCLUDE UNITS IN ALL OF YOUR CALCULATIONS ! ! ! ! ! ! ! ! ! ! !

Accuracy and Precision

accuracy – how close a measured value is to the true or accepted value of the quantity being measured

precision – the degree of exactness with which a measurement is made and stated; reproducibility of results; can relate to the ability of an instrument to produce consistently accurate measurements

Significant Figures or Digits

those digits in a measurement that are known with certainty plus the first digit that is uncertain

also called sig figs or sig digs

Rules for Significant Figures

all non-zero digits are significant zeros between non-zero digits are

significant zeros in front of non-zero digits are

not significant (they are place holders)

zeros that are at the end of a number AND also to the right of the decimal are significant

Rules for Significant Figures

zeros at the end of a number but to the left of the decimal are not considered significant but are important as place-holders (unless you are told that they are measured)

Rules for Significant Figures

123

10203

0.0045

0.004500

15,000

Rules for Rounding

leave the number alone when the digit following the last significant figure is 0, 1, 2, 3, or 4

round up when the digit following the last significant figure is 5, 6, 7, 8, or 9

Special Rules for RoundingThe Symmetric Rounding Rule

This rule is sometimes followed when the digit following the last significant figure is 5. This rule says to round to the nearest even number. This rule is often used to reduce average error due to rounding since the numbers are sometimes rounded up and sometimes rounded down.

Rules for Significant Figures – Adding and Subtracting

when adding or subtracting: the final answer should have the same number of digits to the right of the decimal as the measurement with the least number of digits to the right of the decimal

Rules for Significant Figures – Adding and Subtracting

125. 36 m

+ 17. 205m

142. 565m

142. 57 m

Rules for Significant Figures – Multiplying and Dividing

when multiplying or dividing – the final answer should have the same number of significant digits as the measurement having the least number of significant digits (regardless of where they are in relation to the decimal)

Rules for Significant Figures – Multiplying and Dividing

1 2 5 . 3 m

x 7 . 2 0 m

9 0 2 . 1 6 0 m2

9 0 2 m2

Mathematics – The Language of Physics

physicists make their work easier by summarizing data in tables and graphs and by abbreviating quantities in equations

dimensional analysis can help identify whether a physics expression is a valid one

Mathematics – The Language of Physics

order-of-magnitude calculations provide a quick way to evaluate the appropriateness of an answer