Bell Work: Goal Setting

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# Bell Work: Goal Setting - PowerPoint PPT Presentation

Bell Work: Goal Setting. Locate your goal sheet from January. Pick up a new goal sheet by the basket. Fill in your area averages on the goal sheet from the orange sheet. Fill out the rest of the goal sheet. Remember to choose specific and realistic things to do to improve your grade.

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## Bell Work: Goal Setting

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Presentation Transcript
Bell Work: Goal Setting
• Locate your goal sheet from January.
• Pick up a new goal sheet by the basket.
• Fill in your area averages on the goal sheet from the orange sheet.
• Fill out the rest of the goal sheet. Remember to choose specific and realistic things to do to improve your grade.

Ex: Do review sheet as a practice test; review bell work 2x a week; study with a partner for 30 minutes; answer all lab questions; turn in on time

### Vibrations and Waves

Waves carry energy from one place to another

• Waves temporarily disrupt the medium through which they travel

Energy is transmitted (moved) – matter is NOT transmitted

• Two categories: mechanical and electromagnetic
Electromagnetic Waves
• do not need matter
• perpendicular electric and magnetic fields
• Radio, microwave, infrared (heat), visible light, ultraviolet, x-ray, gamma ray
Mechanical Waves
• need matter to travel
• Cannot travel through a vacuum
Longitudinal Waves
• AKA compressional waves
• matter vibrates same direction as the wave moves (parallel)
• Examples: Sound is created from vibrating objects; AC current
Transverse Waves
• matter moves at a right angle to the movement of energy (perpendicular)
• Examples: guitar string, stadium waves
• video

Practice

Surface Waves
• Surface wave: mixture of both Longitudinal and Transverse; matter travels in circles
• Example: water waves
Wave Speed
• SPEED DEPENDS ONLY ON THE MEDIUM
• Medium is the stuff that the wave travels through – spring, space, air, iron, 55o F water, etc.
Wave Speed
• Sound waves move at 343 m/s in room temperature air, faster in liquids and solids
• Electromagnetic waves travel at speed of light c = 3 x 108 m/s; slower through matter
Transverse WaveAnatomy

crest

crest

amplitude

Matter moves

wavelength

Rest line

Energy moves

trough

λ

trough

Practice

Bell Work: Which wave?
• Which wave has the. . .
• 1. . . most energy?
• . . smallest
• wavelength?
• . . . . . smallest
• frequency?
• 4. . . . . smallest amplitude?
• Which two waves have the same. . . .5. . . . . .amplitude?
• 6. . . . . wavelength?

A

B

C

D

Wave Properties

Measuring Wave Properties

Wave Relationships
• as wavelength increases, frequency decreases (inversely related)
• As wavelength increases, period increases (directly related)
• As frequency increases, period decreases (inversely related)
• Speed only depends on the medium that a wave travels through
• Energy is shown in the amplitude
If a water wave oscillated up and down three times each second and the distance between wave crest is 2 m, what is its frequency?

What is its period?

What is its wavelength?

What is its wave speed?

Shock Wave

http://observe.phy.sfasu.edu/courses/phy101/lectures101/

Sonic Booms
• http://www.physics.sfasu.edu/astro/courses/phy101/SonicBoom.html
What determines the speed of a wave?

(a) the frequency

(b) the wavelength

(c) the amplitude

(d) the period

(e) the medium of transmission

What dictates the frequency of a sound wave?

(a) wavelength

(b) medium

(c) source of the sound

(d) speed

(e) amplitude

Examples of Resonance
• mass on a spring at resonance
• swinging your legs in a swing
• breaking a wine glass using sound
• a singing rod caused by forced vibration
• fog horn
• a tuning fork exciting a guitar string
• In 1940, the Tacoma Narrows Bridge was destroyed by wind-generated resonance.

Tacoma Narrows Bridge

Resonance allows energy to be transferred to a vibrating object efficiently if the energy is delivered at the natural frequency of vibration.