# PHYSICS 231 INTRODUCTORY PHYSICS I www pa msu

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PHYSICS 231 INTRODUCTORY PHYSICS I www. pa. msu. edu/courses/phy 231 Scott Pratt prattsc@msu. edu (517) 355 -9200, ext. 2016 Office Hours: T-R, immediately after class in 4208 A BPS Tuesday: 1: 00 -2: 30 PM in 1248 BPS

Homework • Graded electronically with LON-CAPA http: //msu. loncapa. org • Due Wednesdays at 10: 00 AM • No HW due week after Exam 1 and Exam 3 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

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 platinumiridium 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 2

Dimensional Analysis Checking equations with dimensional analysis: (L/T 2)T 2=L L (L/T)T=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 p) are dimensionless

Example 1. 1 Check the equation for dimensional consistency: Here, m is a mass, g is an acceleration, c is a velocity, h is a length

Example 1. 2 Consider the equation: Where m and M are masses, r is a radius and v is a velocity. What are the dimensions of G ? L 3/(MT 2)

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, nm