1. PHY138 – Waves, Lecture 2 Today’s overview
Hooke’s Law and Oscillation of Springs
Hanging Springs
The Pendulum
Damped Oscillations; Shock Absorbers
Driven Oscillations; Resonance

2. Want to do Research? Pre-Med Society Annual Research Fair
Friday, 3:30
MSB 3153
Learn about research opportunities from representatives of various fields of science, as well as organizations at U of T
—LMP, physiology, immunology, and more!
For more info, visit: or our Facebook group: U of T Pre-Medical Society
Pizza and drinks will be served!

3. Clicker Quiz
Gravitational Potential Energy increases with height. Elastic Potential Energy increases as a spring is stretched. Kinetic Energy increases with speed.
A mass hangs motionless from a spring. When the mass is pulled down and held at rest, the total energy of the mass and spring is
A. larger than before.
B. the same as before.
C. less than before.

4. Reading Assignment
Next week’s reading is Knight Chapter 20, Sections 20.1 – (We are skipping Chapters 15,16,17,18 and 19.) There is a pre-class quiz on for Chapter 20 due on Monday morning.
A Problem Set on Chapter 14 is due on Friday at 11:59PM.
Test 1 will be given back to you at the end of tutorial this week. Marks will be posted on STORM by Wednesday.

8. Two pendula have the same length, but different mass
Two pendula have the same length, but different mass. The force of gravity, F=mg, is larger for the larger mass. Which will have the longer period?
A. the larger mass
B. the smaller mass
C. neither

9. Mass on Spring versus Pendulum
Mass on a Spring
Pendulum
Condition for S.H.M.
Small oscillations
(spring obeys Hooke’s Law)
Small angles
(sinθ ≈ θ)
Natural frequency [rad/s]
Period

10. A person swings on a swing
A person swings on a swing. When the person sits still, the swing oscillates back and forth at its natural frequency. If, instead, two people sit on the swing, the natural frequency of the swing is
A. greater
B. the same
C. smaller

11. A person swings on a swing
A person swings on a swing. When the person sits still, the swing oscillates back and forth at its natural frequency. If, instead, the person stands on the swing, the natural frequency of the swing is
A. greater
B. the same
C. smaller

12. 14.7 Damped Oscillations

14. 14.8 Externally Driven Oscillations
Resonance!