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Thought for the Day

Thought for the Day. Midterm. Friday October 26, 5–7pm room to be determined one person writing early (must email me today). Tutorials/TAs. Tutorials T0101: M 10am, MP 134 T0201: T 10 am, MP 137 Teaching Assistant Jean-S ébastien Bernier. Study groups.

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Thought for the Day

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  1. Thought for the Day

  2. Midterm • Friday October 26, 5–7pm • room to be determined • one person writing early (must email me today)

  3. Tutorials/TAs • Tutorials • T0101: M 10am, MP 134 • T0201: T 10 am, MP 137 • Teaching Assistant • Jean-Sébastien Bernier

  4. Study groups • if you’d like help to find others wanting to form study groups, send me an email LIKE THIS: • Subject: ABC PHY255 study • no content in the body • I’ll send out an email to those people, with all people’s addresses in the To: field (in the clear)

  5. Modelling oscillations

  6. Elements of an oscillator • need inertia, or its equivalent • mass, for linear motion • moment of inertia, for rotational motion • inductance, e.g., for electrical circuit • need a displacement, or its equivalent • amplitude (position, voltage, pressure, etc.) • need a negative feedback to counter inertia • displacement-dependent restoring force: spring, gravity, etc. • electrical potential restoring charges

  7. Hooke’s Law • restoring force proportional to displacement from equilibrium

  8. Oscillation of mass on spring restoring force • x(t) is a function describing the oscillation • what function gives itself back after twice differentiated, with negative constant? • cos(at), sin(at) both do work • exp(at) looks like it ought to work... inertial force equation of motion

  9. Oscillation of mass on spring • frequency determined by spring constant k, and by mass m. • cos(wt+fo) is similar try:

  10. Phasor notation • x(t)=Aexp(iwt+fo) is a solution also try:

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