Project

1
Project

• Boomilever?wooden tower designed to hold maximum
  weight
• Electric vehicle?electric-propelled car designed
  to go a specific distance
• Sounds of Music?build an instrument to play
  specific notes/chords
• Robot Ramble?build a robot to complete a specific
  set of tasks
• Wright Stuff?self-propelled plane to fly furthest
  and/or longest (permission only)

2
Science Olympiad Science Fair

• Egg-O-Naut ? launch an egg on a water-propelled
  rocket and return it safely to Earth
• Electric vehicle ? electric-propelled car
  designed to go a specific distance
• Elevated Bridge ? design and build the most
  efficient bridge to contest specifications
• Its About Time ? build a non-electrical time
  piece
• Trajectory ? design and construct a device
  capable of launching a projectile into a target
  area

3
Pre-Class for Monday 3-26-012

• What is periodic motion? Hint we have covered
  this beforelong time ago.

4
Vibrations and Waves

• Chapter 14

5
Periodic Motion

• Any type of motion that repeats or has a cyclic
  pattern
• Examples pendulum, spring, circular motion
  (including orbital mechanics)
• We will focus on the pendulum and spring
• Assume that all periodic motion is simple
  harmonic motion the force added is directly
  proportional to the distance moved

6

• An object suspended by a string or rope that
  swings back and forth
• Maximum velocity occurs at the bottom of the
  swing (KE)
• Minimum velocity occurs at the top of the swing
  (PE)
• We define the period as the time it takes the
  object to travel from one side to the other and
  back

L length of string (m)
T period (s)
Pendulum
7
Swinging Lab

• Objective
• Find the acceleration of gravity
• Materials
• Pendulum, stopwatch, meter stick, calculator
• Procedures
• Record L for your pendulum.
• Measure the period.
• Solve for g.
• How close to the actual value are you? If less
  than 10, stop otherwise, try again.

8
Pre-Class for Tuesday 3-27-12

• At what point in the swing is the speed of a
  pendulum the greatest?

9

• Metal or plastic shaped in a spiral pattern,
  designed to store/release energy
• When compressed or stretched, elastic potential
  energy is stored
• Amount of force required to store energy is based
  on the spring constant
• Assume all springs obey Hookes Law

Spring
F restoring force (N) k spring constant
(N/m) x distance stretched or compressed (m)
PE stored energy in spring (J)
10
WAVE CHARACTERISTICS

• Waves repeating disturbances that transfer
  energy through matter or space
• Crest highest point of wave
• Trough lowest point of wave
• Amplitude distance from rest position to crest
  or trough

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(No Transcript)
12

• Wavelength (measured in meters)
• Distance between two similar points on a wave
• Frequency (measured in Hertz)
• Number of wavelengths that pass a fixed point
  each second
• Wave speed
• (measured in meters per second)
• How fast a wave is traveling

13

• v l n
• v wave speed (m/s)
• l wavelength (m)
• n frequency (Hz)

14
2 TYPES OF WAVES

• LONGITUDINAL
• (COMPRESSIONAL)
• motion and oscillation are parallel
• ex. Sound

• TRANSVERSE
• motion and oscillation are perpendicular
• ex. Light, radio waves

15
PRINCIPLE OF SUPERPOSITION

• Waves can algebraically interact with each other
• This interaction is called interference
• Destructive waves subtract from each other
• Constructive waves add to each other

16
Ch 14 HW p397- 400

• - 0.12m
• 0.35 J
• 0.21 m
• 0.29 m/s 0.21 s
• 1350 m
• See picture
• 88. 2.4 s

17
Pre-Class for Wednesday 3-28-012
Chapter
15

• What type of wave is a sound wave? List all that
  apply.

1. Longitudinal wave
2. Surface wave
3. Pressure wave
4. Transverse wave

18
Sound (and Music)

• Chapter 15

19

• Intensity (measured in decibels)
• Amount of energy transmitted by a wave
• Loudness (measured in pain)
• Human perception of sound intensity
• Pitch (measured in Hertz)
• The relative high or low frequency of a sound wave

20
Longitudinal wave (sound)

• Must have a medium (material) to travel through
• Points of highest pressure are the crests
• Points of lowest pressure are the troughs
• Distance between crests or troughs is the
  wavelength

http//www.kettering.edu/drussell/Demos/waves/wav
emotion.html
21
How you hear

• Middle Ear has the anvil, hammer, and stirrup.
• Inner ear has the cochlea.

http//www.jimmyr.com/blog/hearingloss.swf
22
Resonant Frequency

• Breaking glass with sound
• http//www.youtube.com/watch?v17tqXgvCN0E
• Tacoma Narrows Bridge
• http//www.youtube.com/watch?vj-zczJXSxnw

23
Doppler Effect

• The change in frequency of a wave due to the
  motion of the source or receiver
• If the wave is moving closer to the receiver, the
  frequency (pitch) increases
• If the wave is moving away from the receiver, the
  frequency (pitch) decreases

24
Doppler Effect Equation

• nd ns (v vd) / (v vs)
• where nd is the detector frequency (Hz)
• ns is the source frequency (Hz)
• v is the speed of sound (m/s)
• vd is the speed of the detector (m/s)
• vs is the speed of the source (m/s)

25
Prandtl-Glauert singularity X http//www.eng.vt.ed
u/fluids/msc/gallery/conden/mpegf14.htm X
http//www.galleryoffluidmechanics.com/conden/b2bg
.htm   http//www.kettering.edu/drussell/Demos/do
ppler/doppler.html   http//www.lon-capa.org/mmp/
applist/doppler/d.htm http//www.youtube.com/watc
h?vTBuIidllusc http//www.youtube.com/watch?vwHr
wgRsX0BI
26

• 1.7 km
• 510 m
• 9.8 x 104 Hz
• 1.45 x 103 m/s
• 20 dB change is equal to 10 times the pressure
  100
• 350 Hz
• 335 Hz 356 Hz
• 280 Hz 263 Hz

Ch 15 HW
p425-428
27
Pre-Class for Friday 3-27-09

• The changing of the frequency based on the
  movement of the source or detector is called the
  _____ _____.

28
Pre-Class for Tuesday 10-21-08

• Reviewing for test.

29
Pre-Class for Tuesday 3-27-12

• What is a pendulum, or what causes a pendulum to
  swing?