What is Physics?

What is Physics?

• Physics is – the scientific study of the physical world:

matter, energy, motion, and force. – The study of the fundamental laws of

nature, which, simply put, are the laws that underlie all physical phenomena in the universe.

• From a Greek term meaning "the science of nature."

What is Physics? Continued

• Physics is everywhere, in fact most people know more about it than they think they do– When you buy ice cream you know that you need to

put it in the freezer. Why? Because it would melt otherwise.

• Any problem that deals with temperature, size, motion, position, shape, or color involves physics.

• We have remarkably found that these laws can be expressed in terms of mathematical equations.

Areas within PhysicsName Subjects Examples

Mechanics Motion and its causes, interactions between objects

Falling objects, friction, weight, spinning objects

Thermodynamics Heat and Temperature Melting and freezing processes, engines, refrigerators

Vibrations and Wave Phenomena

Specific types of repetitive motions

Springs, pendulums, sound

Optics Light Mirrors, lenses, color, astronomy

Electromagnetism Electricity, magnetism, and light

Electrical charge, circuitry, permanent magnets, electromagnets

Relativity Particles moving at any speed, including very high speeds

Particle collisions, particle accelerators, nuclear energy

Quantum mechanics Behavior of submicroscopic particles

The atom and its parts

This is Physics!!

SI UnitsQuantity Name SI Abbreviation

Length Meter m

Mass Kilogram kg

Time Second s

Electric current Ampere A

SI Prefixes• Prefixes are used to change the size of

the base unit. Used instead of writing a lot of zeroes.

Conversion Factors• Conversion factor

– A ratio of equivalent measurements.– Useful in solving problems in which a given

measurement must be expressed in some other unit of measurement.

Dimensional Analysis

• Dimensional analysis– A way to analyze and solve problems using

the units of the measurements.

Converting Between Units

Multistep Problems

Converting Complex Units

Practice Problems

• A minivan sells for 33,200 dollars. Express the price for a minivan in kilodollars and Megadollars?

• A Typical E.coli bacterium is about 5 micrometers in length.Give the length in millimeters and kilometers.

• How many seconds are in a leap year?• Convert the speed 5.30 m/s to km/h.

Scientific Notation

• Scientist often deal with very large or very small numbers. These numbers can be expressed in powers of 10

• Numbers take the form of– M X 10n

• Where M = a number 1 – 10• And n = the number of decimal places moved

Conversions usingScientific Notation with large numbers

• Ex 1 • Convert 1,500,000 to scientific notation.• First move the decimal place so that there is

only one digit to its left• 1.5• How many spaces did we move them?• 6• So we write it as• 1.5 x 106

Conversions using Scientific Notationwith small numbers

• Ex 1• Convert .000025 to scientific notation• First move the decimal• 2.5• How many places did we move it?• 5• So we write it as:• 2.5 x 10-5 (note: since the number was less than

one it is written as a negative number)

Sample Problems

• Convert the following:– 5.65 x 106

– 4.90 x 10-4

– .000000045– .0000067

Using Scientific Notation• Multiplication

– The base numbers are multiplied and the exponents are added.

• (4.0 x 103)(2.0 x 103) =

• Division– The base numbers are divided and the exponents

are subtracted.• (1.06 x 104)/(2.0 x 10-2) =

• Addition or subtraction– Express all the exponents in the same power of

10. Perform the addition or subtraction, then if necessary convert to correct form of scientific notation.

• 7.11 x 104 + 4.0 x 103 =

Significant Figures(Sig Figs)

• All Digits 1-9 are significant– 129 – 3 sig figs

• Zeros between significant digits are significant– 5,007 – 4 sig figs

• Trailing zeros are only significant if the number contains a decimal point– 100.0 – 4 sig figs– 100 – 1 sig fig

• Zeros in the beginning of a number whose only function is to place the decimal points are not significant

– 0.0025 – 2 sig figs

• Zeros following a decimal significant figure are significant– 0.000470 – 3 sig figs– 0.47000 – 5 sig figs

Calculations using Sig Figs

• When multiplying or dividing– Round to the least number of sig figs

• When adding or subtracting – Round to the least amount of decimal

places

Sample Problems

• 6.201 cm + 7.4 cm + .68 cm + 12.0 cm

• 10.8 cm - 8.264 cm

• 139 cm x 2.3 cm

• 18.21 g 4.4 g

Today’s Homework

• Page 9 – 1, 2

• Page 20 – 1, 2, 3,

• Pages 27 – 31 – 1,2,5,7,8,11,13,16,18,19,20,21,22