Welcome to PHYS 253!

What is physics??? Study of the Universe! How it works, where it came from, where it’s going [ rules of the game! ] Study of matter and energy Study of motion (kinematics / dynamics) “reductionist” approach to life The unknown Universe! Physics!

Branches of Physics Mechanics / kinematics Fluid dynamics Study of motion (“Newton!”) Fluid dynamics Thermodymamics Optics Electricity and magnetism Modern physics Quantum mechanics, Relativity, etc…

Measurement and Units Physics is the study of physical things Need to “qualify” what we measure UNITS! USA: Imperial System mph, ft, lbs, US pint, etc… Rest of the world: Système internationale Metric system!

Fundamental SI Units Length: meter (m) Time: second (s) “Distance travelled by light in a vacuum during an interval of 1/299 792 458 seconds” Time: second (s) “Duration of 9 192 531 770 periods of the radiation corresponding to hyperfine transition of Cs-133” Mass: kilogram (kg) “Mass of the prototype kilogram in Paris.”

Les unités de la systeme internationale Distance: mètre (m) “La distance parcouru par la lumière dans un vacuum durant 1/299,792,458 seconds” Temps: seconde (s) “La duration de 9,192,531,770 périodes des radiations du transition hyperfine de Cs-133” Masse: kilogramme (kg) “La masse équivalente de la kilogramme prototypique à Paris.”

Converting Units To switch back and forth from one type of unit to another, multiply by “unit conversion factor” Example: How many feet in 1 km? We know 1 km = 1000 m , and 3.3333 feet = 1 m All units cancel except the one we’re trying to find Units must describe the same quantity! (e.g. can’t convert time to distance)

Additional Example Example: How many seconds are in a year? Solution: We want to convert 1 year = ??? s. Since 1 year = 365.25 days 1 day = 24 hr 1 hr = 60 min 1 min = 60 s we can determine

Compound Quantities and Units All quantities and units are made up of those three! From one unit: Area: Volume: length length w h length w h l

Compound Quantities and Units All other units are made up of those three! Speed: how much distance is covered in a particular amount of time Acceleration: how does speed change over a particular amount of time?

Dimensional Analysis Area: Volume: We can figure out what the compound units are by writing all known quanities in terms of the fundamental SI units! Area: Volume: w h w h l

Dimensional Analysis Speed: Acceleration:

What are the units of force? Example: Acceleration can be expressed as the ratio between the force applied to a mass and the value of the mass: Using dimensional analysis, determine the units of force.