1. Thought for the Day

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

3. Tutorials/TAs Tutorials Teaching Assistant 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 LIKE THIS:
Subject: ABC PHY255 study
no content in the body
I’ll send out an 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
inertial force
equation of motion
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...

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

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