1. Welcome to PHYS 253!

2. 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!

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

4. 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!

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

6. 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.”

7. 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 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)

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

9. 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

10. 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?

11. 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

12. Dimensional Analysis
Speed:
Acceleration:

13. 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.