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PHYSICS 231 INTRODUCTORY PHYSICS I pa.msu/courses/phy231

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 Information. http://www.pa.msu.edu/courses/phy231. Succeeding in Physics 231. Do your homework (yourself)!

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PHYSICS 231 INTRODUCTORY PHYSICS I pa.msu/courses/phy231

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  1. PHYSICS 231INTRODUCTORY PHYSICS Iwww.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

  2. Course Information http://www.pa.msu.edu/courses/phy231

  3. Succeeding in Physics 231 • Do your homework (yourself)! • Use the help room (1248 BPS) ! • Make sure you understand both “why” and “why not” • Interrupt the lecturer!

  4. General Physics • First Semester (Phy 231) • Mechanics • Thermodynamics • Simple harmonic motion • Waves Second Semester (Phy 232) • Electromagnetism • Relativity • Modern Physics • (Quantum Mechanics, …, etc.)

  5. Mechanics • Half the course • Quantified largely by Galileo • Problems involve:velocity, acceleration, mass, momentum, energy, torque, angular momentum, moment of inertia…

  6. UNITS (Systéme Internationale)

  7. Standard Kilogram at Sèvres

  8. Dimensional Analysis Dimensions & units can be treated algebraically.

  9. Dimensional Analysis Checking equations with dimensional analysis: (L/T2)T2=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

  10. 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

  11. Example 1.2 Consider the equation: Where m and M are masses, r is a radius andv is a velocity. What are the dimensions of G ? L3/(MT2)

  12. Example 1.3 Given “x” has dimensions of distance, “u” has dimensions of velocity, “m” has dimensions of mass and “g” has dimensions of acceleration. Is this equation dimensionally valid? Yes Is this equation dimensionally valid? No

  13. 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

  14. Example 1.3 Grandma traveled 27 minutes at 44 m/s. How many miles did Grandma travel? 44.3 miles

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

  16. Example 1.4a The above expression yields: 40.11 m 4011 cm A or B Impossible to evaluate (dimensionally invalid)

  17. Example 1.4b The above expression yields: 4.5 m kg 4.5 g km A or B Impossible to evaluate (dimensionally invalid)

  18. 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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