{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

p140w07_ct_24

# p140w07_ct_24 - Physics 140 Winter 2007 Lecture#23 Dave...

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

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

View Full Document

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

View Full Document

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

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Physics 140: Winter 2007 Lecture #23 April 10, 2007 Dave Winn Racquetball Striking a Wall Copyright: Loren M. Winters Mt. Etna Andrew Davidhazy Predicting the speed of waves • Speed must be set by some combination of coupling between oscillators and inertia • Waves on a string: tension vs. linear density v = √ (T / λ ) • Sound waves: compressibility vs. density v = √ (B / ρ ) • Usually: frequency of waves determined by an outside disturbance (like me) • Wavelength is then determined by how fast waves “run away” from the point of disturbance: fast waves => large λ The speed of waves on a string is set by the tension and the mass per unit length. I send waves of frequency f down the string which is under tension T , I get waves with wavelength λ . What happens if I double the tension; how does the wavelength change? 1: λ < λ 2: λ = λ 3: λ > λ Disturbances of all kinds take time to travel. When I release this slinky, it takes time for the release of the end to travel to the bottom. As a result, the slinky all gathers together first, then falls to the floor… Mathematical description of waves • Consider a sinusoidal wave • Wave peaks are when • Written in a slightly different way: • Peaks move to the left ( ) f 2 2 sin ) , ( π ω λ π ω = = − = k t kx A t x y f k v t k x t kx λ ω π ω π ω = = + = = − 2 or 2 Positive v, travels to the right… ( ) t kx A t x y ω + = sin ) , ( k t k x t kx 2 2 π ω π ω + − = = + Negative v, travels to the left An example • Consider this wave • Wavelength • Frequency • Wave speed ( ) t x t x y 5 . 4 . 3 sin . 4 ) , ( + − = . 3 2 . 3 2 − = − = = π λ λ π k π π ω 2 5 . 4 5 . 4 2 = =...
View Full Document

{[ snackBarMessage ]}

### Page1 / 26

p140w07_ct_24 - Physics 140 Winter 2007 Lecture#23 Dave...

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

View Full Document
Ask a homework question - tutors are online