9/11/2014

Physics is Awesome and Physics is Weird

The first law of thermodynamics

by Mike Eats

When a candle is placed into a graduated cylinder, it becomes extinguished. When a candle is placed into a graduated cylinder and then another cylinder is placed inside, it creates a cycle. In this cycle the CO2 produced by the reaction from the flame and burning wax rises due to the heat and outside of the cylinder oxygen is pulled through by the raised temperature, causing a cycle which will keep the candle lit.

a Candle that is lit, inside of a large jar is then dropped, what will happen to the flame?
My group said it would burn more brightly.
We were wrong.
Because the static heat of the flame is lost when the candle is in free fall, The flame can no longer rely on convection for heat to speed up the chemical reaction. It must rely on diffusion which is not as fast a reaction for burning.

The spring is an example of a negative work reaction. Alone the spring does no work and just sits in equilibrium, only when work is applied to the spring to contract it is the spring able to do work.
Similar to a spring is a cylinder of gas at standard temperature and pressure. If work is applied to it, like a spring it can do work in return; likewise, if it is heated it can also produce work. 

This a review of the relationships between pressure, volume and temperature.
This shows the direct relationship between volume and temperature and between temperature and pressure.
This also shows the inverse relationship between pressure and volume.

These equations reflect the previous graphs. These two equations reflect the relationship between volume and temperature (#4) and also pressure and temperature (#5).  Using the ideal gas law and treating all the other portions of the equation as constant, this is an introduction to processes in which either the volume, temperature, or pressure is constant.

This final equation is using the relationship between pressure and volume when temperature is constant. This is a difficult situation as both pressure and volume must change without temperature changing, which though may be negligible is not necessarily constant.

This equation is calculating  work in a system without knowing temperature. In this case it is a water tower and it is lifting water using a change in pressure due to the heat. In this cause the equation for work is delta U. Because temperature is unknown the equation for work is P1V1 multiplied by the natural log of V2/V1. Much physics very wow.

This is the total work, it includes the work done by the the gas and work done by the fluid and finally work done by the mass of the water lifted.
The work done by the mass of the water is equal to mgh
the work done by the gas is PairVtln4
The work done by the air is 1/4PairVt
as the work  done by the mass is positive and the work done by the gas is in the same direction, it is the sum of those two subtracted by the work done by air.
air is the fourth derivative of displacement.

These are the graphs of pressure vs volume, and they identify the four processes that make up a heat engine. When temperature is constant and delta U is zero; it is an isothermal process. When pressure is constant the graph is a horizontal line and it is called isobaric. When volume is constant and W=0 the graph is a vertical line is called isobaric. The final equation is when Q is 0 and that is called adiabatic, the word is similar to Diablo, which is Spanish for the devil.

An example of a heat engine. It is important to recognize that in this engine it is only made up of isobaric and isochloric processes. Next the W and the Q and the delta U is all calculated for each step as well the energy for each step is looked at in each step. In this case energy is 3/2PV.

This board is the culmination of all the findings as well as the equation for efficiency.

This is the equation for efficiency, Conceptually it is the amount of work you get done by the amount of heat you put into the system. that being said the perfect engine would be rated at 1. This is the rating on the engine of the 2006 Chevy Colorado.

This is the practical application for a common efficiency of a heat engine.

This gas law apparatus is creating an environment with constant temperature. Because constant temperature is difficult to achieve, the experiment is not done tracking the pressure and volume over time, but at instantaneous moments.

This is using the previous device to calculate work. Because work is equal to the integral of P with reference to Volume, then pressure must be defined with regards to volume. This becomes the integral of nRT over V. nRT is all constant so it just becomes the natural log of the final volume divided by the initial volume.

#physics.
This is an example of a cycle and the idea of using heat to contract rubber and then allowing it to cool to expand.

Gas Law and Kinetic Theory

by Michael Pryor

This is a representation of the conservation of energy. This is a very poor example, because the light bulb cannot charge the battery. A better example would be to view the Q as something that either produces or gives off heat specifically and then something that either takes work or does work itself. Although the light bulb does give off heat, it is not a good example of its change in energy. An oven is a good example of a change in temperature, but a poor example of doing work, because the work does is not visually apparent. 

In the perspective of the gas laws, work is equal to pressure of a change in volume.
Given that pressure is constant, then the change in volume can be displayed as the change in volume due to the coefficient of heat expansion. The initial volume is the mass divided by the density.
The mass is calculated using the specific heat and the change in temperature.
This shows that because of the density of this object the heat that the object absorbs is much greater than the work that the object does in its expansion due to its change in energy.

Force is equal to the change in pressure over an area. This means pressure is also equal to a force over an area.
If the mass is constant then force is equal to the mass multiplied by the change in velocity, or the velocity squared divided by its displacement.
 Given that the area is a square, its formula is is x squared.
The new formula becomes the sum of the mass multiplied by velocity in one direction squared all divided by the displacement (x) cubed.
The numerator is very similar to the formula for kinetic energy. If that adjustment is made to include the kinetic energy of a an atom in a gaseous state, then the numerator must be multiplied by two and the number of atoms must be accounted for, The atom moves in three dimensions, this means that there is an adjustment of 3. This is proved when you calculate the magnitude of the cube and you make all three dimensions equal, as in a cube.

 Given the initial equation that PV=2/3N*E=N*Kb*T where Kb is the Boltzman constant.
Kinetic energy can be equated to 3/2*Kb*T and that can be equated to 1/2*m*(v)squared
Velocity is then equal to the square root of (3*Kb*T)/m
If Q is equal to W then there is no change in the energy of the system.
Which means the equation is in equilibrium and any fluctuation are met with equal values on either side of the equation.
Given a constant pressure and a constant number of molecules. The question can be redced to 3/2*The change in temperature/actual temperature=the opposite of the change in volume/actual volume
When both sides are integrated, the temperature to the -3/2 power is equal to the volume.

These calculations better represent the calculation of force from a change in pressure over a change in temperature, From the earlier equation in which force equals the change in mass multiplied by velocity plus the change in velocity multiplied by mass.

In this experiment the change in volume equates to a change in temperature. As the volume decreases then temperature must increase, because there is no significant change being done to the energy in the system.
Theoretically the final temperature inside the syringe is 604 K this is a significant jump from its original temperature of
293 K and is enough to light a small piece of cotton on fire inside of the syringe.

Physics like a Boss.

Ideal Gas Law 

A hypothesis on the experiment of filling a can with steam and then placing it in a cool water bath upside down so that the opening is completely submerged.

The conclusion to the experiment: when the opening of the can was free of the water bath, the change in phase of the steam to water caused the can to implode.

An experiment using a manometer to determine the density of water.

The conclusion: by measuring the height that the water ascends to in the manometer and calculating the volume of the column 

A bell jar is sealed and the pressure is decreased inside, what will happen to the marshmallows?

The predictions of the group about what would happen during and after the experiment.
Conclusion: The marshmallows did expand but when the bell jar was purged and the pressure returned to room pressure the marshmallows shrank and became small and wrinkly.

An experiment in which a tube is ran through a pressure sensor and on the other end of the tube is a syringe. As the plunger is depressed and the volume inside the syringe decreases the sensor monitors the change in the pressure inside the tube.

Pressure (kPa) vs Volume (mL)

This experiment shows the relationship between temperature and volume by placing a stopper and a tube over the opening in a flask and attaching the other end of the tube to a syringe. When the temperature inside the flask changes, the volume inside the syringe will adjust as well.

Temperature (C) vs. Volume (cc)

The relationship between Temperature and Volume is linear (Y=X)

This experiment shows the relationship between temperature and pressure. The same vial is used that has a stopper and a tube in it, this time the tube is connected to a pressure sensor and as the vial heats up the pressure sensor adjusts accordingly.

Temperature (C) vs Pressure (kPa)

Pressure (kPa) vs Temperature (C)

The relationship between Pressure and Temperature is linear (Y=X)

Thermal Expansion

A meter long rod of unknown material is being heated by steam.

The change in radius of the bar by measuring angular velocity.

Calculations for energy lost in fusion, heating, and boiling.

The calculations showing that the coefficient of thermal expansion is similar to that of steel.

The steps and specific values and calculations for transfer of heat lab

The experimental set up

The graph of heat vs time. Showing specifically time when ice was present and when the temperature leveled off at the boiling point.

Uncertainty for the Latent Heat of Fusion (J/g)

Uncertainty for the Latent Heat of vaporization (J/g)

the uncertainty for the specific heat of water

The percent deviation from the accepted values. The Latent Heat of Fusion is off by 20% because of the inability to take into account the energy spent in the water or the rate of change from the ice into the water. The Latent Heat of Vaporization is off because the Logger Pro stopped recording before the heat was finished transferring throughout the water.

A video showing that heat is causing the ring to expand, so that the cool ball can fit through.

Heat causes brass to expand faster than the substance opposite it when heat is applied directly to the brass.

The brass still expands faster even when the heat is applied to the substance opposite it.