PHYSICS 231INTRODUCTORY PHYSICS I

www.pa.msu.edu/courses/phy231

Scott Prattprattsc@msu.edu

(517) 355-9200, ext. 2016Office Hours:

T-R, immediately after class in 4208A BPS

Tuesday: 1:00-2:30 PM in 1248 BPS

Strosacker Center, 1248 BPS Bldg.Strosacker Center, 1248 BPS Bldg.

• Monday 9:00 AM - noon, 12:30-6:00 PM• Tuesday 8:30 AM - 6:00 PM• Wednesday 8:30 AM - 10:00 AM

•Graded electronically with LON-CAPAhttp://msu.loncapa.org

• Due Wednesdays at 10:00 AM• No HW due week after Exam 1 and Exam 3

HomeworkHomework

EXAMS

• 4 Midterms (on Thursdays during class time)• 1 Final• 11 questions one each midterm, graded on scale of

10• Drop lowest of 4 midterms, no make-ups• 22 questions on final, graded on scale of 20• Exams are closed book - closed note• Midterms will have HIGH overlap with homework• Midterms 2, 3 and 4 will include problem from

previous midterm• Final will be made of reworded Midterm problems

GRADES

4 Midterms 60% •Feb. 5, Mar. 4, Apr. 1, Apr. 29•During class in 1410 BPS (right here)•Lowest score dropped•No makeups•11 questions, graded on scale of 10•Questions largely from homework

Final Exam 30% •May 4, 5:45-7:45 PM, location TBA•22 questions, graded on scale of 20•Reworded Midterm problems

Homework 10% •LON-CAPA, www.loncapa.org•Log-in with pilot ID & password

Textbook

• Serway and Faughn• Old editions are fine

Succeeding in Physics 231

• Do your homework!• Use the help room (1248 BPS) !

Stay away from ALLMSU• Make sure you understand both “why” and

“why not”• Interrupt the lecturer

General Physics

• First Semester (Phy 231)• Mechanics• Thermodynamics• Simple harmonic motion• Waves

Second Semester (Phy 232)• Electromagnetism• Relativity• Modern Physics • (Quantum Mechanics, …,

etc.)

Mechanics

• Half the course• Quantified largely by Galileo• Problems involve:

velocity, acceleration, mass, momentum, energy, torque, angular momentum, moment of inertia…

UNITS (Systéme Internationale)Dimension SI (mks) Unit Definition

Length meters (m) Distance traveled by light in 1/(299,792,458) s

Mass kilogram (kg) Mass of a specific platinum-iridium allow cylinder kept by Intl. Bureau of Weights and Measures at Sèvres, France

Time seconds (s) 9,192,631,700 oscillations of cesium atom

Standard Kilogram at Sèvres

Dimensional Analysis

Dimensions & units can be treated algebraically.

Variable from Eq.

x m t v=(xf-xi)/t

a=(vf-vi)/t

dimension L M T L/T L/T2

Dimensional Analysis

Checking equations with dimensional analysis:

2

21attvxx iif

L (L/T)T=L

(L/T2)T2=L

• Each term must have same dimension• Two variables can not be added if dimensions are different• Multiplying variables is always fine• Numbers (e.g. 1/2 or ) are dimensionless

Example 1.1

Check the equation for dimensional consistency:

2

2

2

)/(1mc

cv

mcmgh

Here, m is a mass, g is an acceleration,c is a velocity, h is a length

Example 1.2

L3/(MT2)

Consider the equation:

2

2

r

MmG

rv

m

Where m and M are masses, r is a radius andv is a velocity.What are the dimensions of G ?

Units vs. Dimensions

• Dimensions: L, T, M, L/T …• Units: m, mm, cm, kg, g, mg, s, hr, years …• When equation is all algebra: check

dimensions• When numbers are inserted: check units• Units obey same rules as dimensions:

Never add terms with different units• Angles are dimensionless but have units

(degrees or radians)• In physics sin(Y) or cos(Y) never occur unless

Y is dimensionless

Example 1.3

Grandma traveled 27 minutes at 44 m/s.How many miles did Grandma travel?

44.3 miles

Prefixes

In addition to mks units, standard prefixes can be used, e.g., cm, mm, m, nm