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PAL # 11 Doppler
b)Detector toward, Source toward:f’ = f ( v+vD / v-vS )
for vD = 3 m/s, f’ higher
d) Detector away, Source toward:
f’ = f ( v-vD / v-vS )
for vD = 3 m/s, f’=f
c) Detector away, Source away:f’ = f ( v-vD / v+vS )
for vD = 3 m/s, f’ lower
e) Detector toward, Source away:
f’ = f ( v+vD / v+vS )
for vD = 3 m/s, f’=f
Thermodynamics
Thermodynamics deals with the internal energy of a system
We will examine how this internal energy changes due to changes in heat and work
One of the important concepts in thermodynamics is temperature
How do we experience temperature?
Thermoscope Changes in temperature cause changes in other
properties
We can measure these changes to construct a thermoscope, a device to record changes in temperature
The oven is at a higher temperature than the refrigerator Temperature changes are caused by an exchange of
heat
Thermal Equilibrium When the thermoscope stops changing, it
and the water are in thermal equilibrium
If we move the thermoscope to a different cup and it reads the same value we know that it and the second cup are also in thermal equilibrium
Zeroth Law of Thermodynamics
What happens if we pour the two cups together? The cups are in thermodynamic equilibrium
with each other
If two objects are each in thermal
equilibrium with a third object then they are also in thermal equilibrium with each
other
Thermometers
In order for a thermoscope to be a thermometer if needs to be calibrated
For example, the Celsius scale
Them put the tube in boiling water and mark that mercury level “100”
You now have a Celsius thermometer
The Kelvin Scale
The Kelvin scale is designed so that 0 K is at absolute zero and that 273.15 K is at the freezing point of water
TC = TK -273.15
The Triple Point of Water
The triple point of water is the only temperature where water can exist in liquid, solid and gas forms simultaneously
Converting Temperatures
A temperature change of 5 Celsius degrees is equal to a temperature change of 9 Fahrenheit degrees
Temperature Scales
Gabriel Daniel Fahrenheit invented the mercury thermometer in 1714
Anders Celsius introduced his scale is 1742
William Thomson, Lord Kelvin, determined from theory that minus 273.15 degrees Celsius is the coldest it can get
Thermal Expansion Some objects expand more than
others when heated
The degree of expansion depends on the change in temperature and the coefficient of expansion
Linear Expansion The degree to which the length of an object
changes is given by:L = L T
This applies to all dimensions of a solid length,
width and height
Two strips of metal with different coefficients of linear expansion attached together
This principle is used in dial thermometers and thermostats
Volume Expansion If the linear dimensions of a solid change
then the volume must change:
Where =3
Density in general decreases with increasing temperature
Temperature and Heat
Temperature is a measure of the internal (thermal) energy of a system
Heat (Q) is energy transferred between systems due to a temperature difference
Heat can manifest itself in different ways
Being “hot” does not mean you have a lot of “heat”
Heat
The rate of heat exchange depends on the temperature difference Run warm water over your hands after being
outside on a cold day and the water feels hot
You feel hot on a hot day because your body generates heat and can’t get rid of it quickly enough