# PHYSICS 231 INTRODUCTORY PHYSICS I www.pa.msu.edu/courses/phy231 Scott Pratt pra

## PHYSICS 231 INTRODUCTORY PHYSICS I www.pa.msu.edu/courses/phy231 Scott Pratt pra

Barber, Phil, Football Reporter has reference to this Academic Journal, PHwiki organized this Journal PHYSICS 231 INTRODUCTORY PHYSICS I www.pa.msu.edu/courses/phy231 Scott Pratt prattsc@msu.edu (517) 355-9200, ext. 2016 Office Hours: Monday, 9-10:30 AM in 1248 BPS Course In as long as mation http://www.pa.msu.edu/courses/phy231 Succeeding in Physics 231 Do your homework (yourself)! Use the help room (1248 BPS) ! Make sure you underst in addition to both why in addition to why not Interrupt the lecturer!

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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)

St in addition to ard Kilogram at Sèvres Dimensional Analysis Dimensions & units can be treated algebraically. Dimensional Analysis Checking equations with dimensional analysis: 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 p) are dimensionless

Example 1.1 Check the equation as long as dimensional consistency: 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: Where m in addition to M are masses, r is a radius in addition to v is a velocity. What are the dimensions of G Example 1.3 Given x has dimensions of distance, u has dimensions of velocity, m has dimensions of mass in addition to g has dimensions of acceleration. Is this equation dimensionally valid Yes Is this equation dimensionally valid No

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 Gr in addition to ma traveled 27 minutes at 44 m/s. How many miles did Gr in addition to ma travel 44.3 miles Prefixes In addition to mks units, st in addition to ard prefixes can be used, e.g., cm, mm, mm, nm

Example 1.4a The above expression yields: 40.11 m 4011 cm A or B Impossible to evaluate (dimensionally invalid) Example 1.4b The above expression yields: 4.5 m kg 4.5 g km A or B Impossible to evaluate (dimensionally invalid) Example 1.4b The above expression yields: -1.5 m -1.5 kg m2 -1.5 kg Impossible to evaluate (dimensionally invalid)

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