p140w07_ct_20

# p140w07_ct_20 - Racquetball Striking a Wall Copyright:...

This preview shows pages 1–7. Sign up to view the full content.

Physics 140: Winter 2007 Lecture #20 March 21, 2007 Dave Winn Racquetball Striking a Wall Copyright: Loren M. Winters Mt. Etna Andrew Davidhazy

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Simple Harmonic Motion Review • Motion around stable equilibrium • Restoring force like Hooke’s law: F = -kx • Oscillations are harmonic x = Acos( ω t) ω = (k/m) • Energy in oscillations: trading elastic potential and kinetic energy – PE = 1/2kx 2 = 1/2kA 2 cos 2 ( ω t) – KE = 1/2mv 2 = 1/2m ω 2 A 2 sin 2 ( ω t)
Consider a mass on a spring. Any real spring has some mass. When this mass is taken into account, what will happen to the period of oscillation of the spring/mass system? 1: The period will increase 2: The period will decrease 3: The period will remain the same The amount of restoring force remains the same, but the overall inertia is increase. This slows the oscillations.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Imagine a mass which oscillates on an ideal massless spring. If I start the system moving with an amplitude A 0 , it oscillates with an angular frequency ω 0 . Now I start the system again, this time with an amplitude of 2A 0 . What is the angular frequency of oscillation now? 1: ω new = 2 ω 0 2: ω new = 4 ω 0 3: ω new = ω 0 4: ω new = ω 0 / 2 5: ω new = ω 0 / 4 Frequency of oscillation is unrelated to amplitude!
Oscillations with friction… • Real oscillations eventually stop; energy is lost to friction • Oscillation amplitude gradually dies away as energy is drained off • Rate of fading depends on amount of friction, restoring force, and inertia

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
One specific possibility… • If the friction depends on velocity
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 04/04/2008 for the course PHYSICS 140 taught by Professor Evrard during the Fall '07 term at University of Michigan.

### Page1 / 20

p140w07_ct_20 - Racquetball Striking a Wall Copyright:...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online