Final: Tuesday, April 29, 7pm, 202 Brookscommunity.wvu.edu/~miholcomb/Final Review, latest...
Transcript of Final: Tuesday, April 29, 7pm, 202 Brookscommunity.wvu.edu/~miholcomb/Final Review, latest...
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Final: Tuesday, April 29, 7pm, 202 BrooksMakeup Monday April 28, 1pm, 437 White Hall
• 67% focused on this last section of the course
• Chapters 10.1-3, 11.1-2, 11.4-5, 13 (all), 14.1-5, 5.4
• There will also be problems from Chapters 1-7
(motion, forces, energy, momentum, rotation)
• Totaling 25 multiple choice questions
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You should be able to convert between
K/C/F temperature scales
• Fahrenheit to Celsius
– TF = TC x (9/5) + 32
– TC = (TF - 32) x (5/9)
• Kelvin to Celsius
– TK = TC + 273.15
– TC = TK - 273.15
Not a simple factor conversion
∆∆∆∆TC = ∆∆∆∆TF *5/9
∆∆∆∆TC = ∆∆∆∆TK For more problems on Ch. 10 & 11, see lectures
and following problem solving day
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You should be able to calculate the
amount of thermal expansion
• Length expansion
(thermometer)
∆L=αLo∆T
• Area expansion (ring)
∆A=γAo∆T
• Volume expansion
(basketball) ∆V=βV∆T
• Note: ∆T is in °C (or K)
• Note: γ =2α, β= 3α Thermometers rely on a thermal
expansion of a liquid (e.g. mercury)
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Main Ideas in Chapter 11
You should be able to:
• Understand the ways to transfer heat (mostly conceptually except conduction)
• Calculate heat necessarily to raise the temperature or change the phase of a material
Extra Practice: 11.1, 11.3, 11.5, 11.7, 11.9, 11.15, 11.17, 11.25, 11.27, 11.33
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Phase changes (e.g. solid to liquid)
When heating ice into water and then into steam the temperature does not go up uniformly
–Different slopes since cwater > cice
–Flat bits at phase changes
Time
Tem
pe
ratu
reice
water
steam
Melting Point
Boiling Point
Q = m c ∆∆∆∆Tc called the specific heat of a material
cwater = 4190 J/(kg K) - difficult to heatcice = 2090 J/(kg K)
Applying constant heat per second
mLv
mLf
Lf<Lv
https://www.youtube.com/watch?v=lTKl0Gpn5oQ
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Transferring heat energy
• 3 mechanisms
– Conduction
• Heat transfer through material (rods, windows, etc.)
– Convection
• Heat transfer by movement of hot material (hot air, hot
liquid while cooking)
– Radiation
• Heat transfer by light
(sun, fire, tanning bed)
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Rate of heat flow
(Conduction)
Energy flows from higher temp. to lower temp. (0th law)
Rate of energy transfer (P=power) depends on
– Temperature difference (TH-TC)
– Area of contact (A) and length (L) over which heat flows
– Thermal conductivity of the material (k)
• k (copper) = 385 W/(m K) good conductor
• k (air) =0.02 W/(m K) good insulator
• Higher k means more heat flow
- P in Watts, Q in Joules, t in seconds
L
TTkA
t
Q CH −=
∆=P
L
L
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Main Ideas in Chapter 13
You should be able to:
• Understand Simple Harmonic Motion (SHM)
• Determine the Position, Velocity and Acceleration over time
• Find the Period and Frequency of SHM
• Relate Circular Motion to SHM
Extra Practice: C13.1, C13.3, C13.11, 13.1, 13.3, 13.5, 13.9, 13.11, 13.17, 13.19, 13.21, 13.23, 13.25, 13.27, 13.31
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Period and Frequency Independent of Amplitude
• Period of a spring
– The period (T) of a mass on a spring is dependent upon the
mass m and the spring constant k
• Frequency
– The frequency, ƒ, is the number of complete cycles or
vibrations per second; units are s-1 or Hertz (Hz)
k
m2T π=
T
1ƒ =
• The angular velocity is related to the frequency
• The angular velocity/speed (or angular frequency)gives the number of radians per second
m
kƒ2 =π=ω
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Graphical
Representation
of Motion
When x is a maximum or
minimum, velocity is zero
When x is zero, the speed is
a maximum (slope of x)
Acceleration vs. time is the
slope the of velocity graph.
When x is max in the
positive direction, a is max
in the negative direction
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Velocity as a Function of Position
• Conservation of Energy allows a calculation of the
velocity of the object at any position in its motion
– Speed is a maximum at x = 0
– Speed is zero at x = ±A
– The ± indicates the object can be traveling in either
direction
( )2 2kv A x
m= ± −
2
212
212
21 kAkxmv =+
22
max
2
212
max21
Am
kv
kAmv
=⇒
=
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More Ideas in Chapter 13
You should be able to:
• Understand the pendulum
• Determine different kinds of waves
• Find the wavelength, frequency and speed of a wave
• Damped Oscillations
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The Simple Pendulum
xL
mgF −=
Since restoring force is proportional
to negative of displacement,
pendulum bob undergoes SHM.
Effective “spring constant” is
keff = mg/L
effk
mT π2=
g
LT π2=
spring pendulum
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Pendulum
If a pendulum clock keeps perfect time at the
base of a mountain, will it also keep perfect
time when it is moved to the top of the
mountain? If not, will it run faster or slower?
No, g is slightly smaller at higher
altitude.
g
LT π2=
T will be bigger so it will take longer
to complete an oscillation.
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Types of Waves
traveling wave
Transverse
Longitudinal
fv λ=
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Are you on the right wavelength?
6 m/s 2 m
If the wave below has a velocity of 6 m/s, answer the following:
What is the wavelength?
What is the wave’s period?
What is the wave’s frequency?
2 m
T= λ/v = 2 m/(6 m/s) = 0.333 s
f =1/T = 1/0.333s = 3 Hz
fT
v λλ
==
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Main Ideas in Chapter 14
You should be able to:
• Explain how a vibrating object
affects the nearby air molecules
to produce sound waves
• Calculate the speed, intensity
and decibels of sound
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A man shouts and
hears his echo off a
mountain 5 seconds
later. How far away
is the mountain?
Speed of sound ~343m/s at room temperature
Compare to thunder
Determining distance
with echoes
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One of the loudest sounds on Earth was made by the
volcanic eruption of Krakatoa in Indonesia in August
of 1883. At a distance of 161 km, the sound had a
decibel level of
180 dB. How far
away from the
source would
you be to not
experience pain
(<120 dB).
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θθθθ = 35°
m= 12 kg
D = 3m
A 12 kg block slides 3 m from rest down a
frictionless ramp with an incline angle of 35°
before being temporarily stopped by a spring
with spring constant k=30,000 N/m. By how
much is the spring compressed when the block
stops?
How should we
approach this
problem?
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A spring with spring constant 300 N/m is
attached to an object whose mass is 2.0 kg.
If the spring is initially stretched A=0.25 m,
what is the velocity of the object at x = 0, -A
and A/2?
2
212
212
21 kAkxmv =+
( )2 2kv A x
m= ± −