PHYSICS Introduction

What is Science - systematic knowledge of the physical or material world gained through observation and experimentation.

What is Physics? - the science that deals with matter, energy, motion, and force.force - The Rules of Nature.

Hypotheses – tentative and testable statements that must be capable of being supported or not supported by observational evidence. To be accepted as a good hypothesis, there must exist a test or experiment to try and prove it wrong. Theory - based on natural and physical phenomena and are capable of being tested by multiple independent researchers. Unlike hypotheses, scientific theories are well- established and highly- reliable explanations, but may be subject to change as new areas of science and new technologies are developed

Independent variable – factor that is adjusted by the experimenter to see what effect the change has on the dependent variable Dependent variable – factor whose value changes because of a change in the independent variable

Inference – a reasonable conclusion or possible hypotheses based on observations Observation - A conclusion or data gathered, based upon directly observing something. - Observations can be made with eyes, ears, nose, or touch.

Distance The entire linear distance traveled despite side trips Displacement The distance between points “A” and “B”. “As the crow flies” From A to B = 250 m From A to B = 40 m Point A Point B Point A Point B

LAWS-describe the relationships between various phenomena

Boyle’s Law Charles’ Law Cole’s Law

Scientific Law- expressed by words Laws in physics- expressed by math equations

THEORY- reasonable explanation of observed events that are related.

Theories often involve models. e.g. Atomic Theory Democritus’ Model Thomson’s Model Rutherford’s Model Bohr’s Model Electron Cloud Model

Experiments test theories.

Physical Science the study of the physical universe.

The two main branches are physics and chemistry.

These two overlap; the main difference is that physics always deals with the concept of energy.

The major areas within Physics are: mechanics, thermodynamics, waves, optics, electricity and magnetism, relativity, and nuclear physics.

Scientific Method Five Steps State Problem Research it Hypothesis - extends thinking beyond known facts Experiment Draw Conclusions

Certainty in science One should always question the validity of scientific Laws, Theories, or Hypotheses.

METRIC SYSTEM - uses a decimal basis for multiples and fractions of the basic units of measure.

International System of Units = The SI system

Units of measure are used to describe physical quantities. e.g. the meter is the unit of length

Seven fundamental units of measure: 1. length meter 2. masskilogram 3. timesecond 4. electric currentampere 5. temperaturekelvin 6. amount of substancemole 7. luminous intensitycandela

Combinations of these units are used to measure other physical quantities. (e.g. mass density) These are called derived units.

METER Standard meter was a metal bar until Now 1 meter = the distance light travels in a vacuum in 1/ th of a second.

FORCE AND WEIGHT Newton is the accepted unit. Force needed to accelerate a one kilogram mass by one m/s 2.

THE SECOND one second = vibrations of cesium-133 atoms.

1 ml H 2 O = 1 cm 3 H 2 O = 1 g H 2 O or… 1 ml = 1 cm 3 = 1g heat required to change temp of 1 g liquid of H 2 O 1° centigrade (Kelvin) is 1 calorie

ACCURACY - the closeness of a measurement to the accepted value for a specific physical quantity.

absolute error- actual difference between the accepted value and the measured value.

E a = (O – A), where Ea is the absolute error, O is the observed value, and A is the accepted value.

Relative Error - expressed as a percentage. (often called percentage error)

E r = (E a / A) x 100% where E r is the relative error, E a is the absolute error, and A is the accepted value.

PRECISION - the agreement among several measurements that have been made in the same way.

Precision is expressed in terms of DEVIATION.

Absolute deviation- difference between a single measured value and the average of several measurements made in the same way.

Relative Deviation- the percentage average deviation of a set of measurements.

Is this Accurate, Precise, Both, or Neither

SCIENTIFIC NOTATION M 10n M is a number greater than or equal to 1, but less than 10. n is the number of places the decimal point has been shifted. Moved left, n is pos. Moved right, n is neg.

Order of magnitude. numerical approximation to the nearest power of ten.

DATA, EQUATIONS, GRAPHS, DIMENSIONAL ANALYSIS.

Scalar quantities. quantities expressed by single numbers with appropriate units. Vector quantities. Quantities that require magnitude and direction. Usually depicted by arrows.

Two vectors that act on the same point are called components.

RULES OF PROBLEM SOLVING

1. Carefully find what is being asked. Write down all given data.

2. Write down all the symbols and units for the quantities called for.

3. Write down the basic equation relating the known and unknown quantities.

4. Solve for the unknown quantity to find the working equation.

5. Substitute the given data into the working equation.

6. Perform the mathematical operations with the units alone. Unit analysis Dimensional analysis

7. Perform the math

8. Check the answer for reasonableness

9. Review the entire solution.