week 5 day 2

There were not many pictures this day, a lot of people were sick that day, so was our professor. 

we looked at greek letter landa which represents the linear object. We integrated to get E=kQ/d(L+d)

When a point particle went through two rod with charges.

Then we looked into torque.

Lastly, we considered the electric field of objects.

week 5 day 1

We looked at electric field this time. It follows E=F/q. Then we substute F=kq1q2/r^2/q to get E=kq/R^2.

In real situation, charges are in three dimension. We graphed it.

We also did it in vpython.

We then calculated some electric field due to two point charges.

We calculated the electric field.

We did it in an excel spreadsheet to calculate the electric field due to a charged rod.

Week3 day 1

We looked into some depth of the equation PV=nRT

We broke down the relationship among PVT in different conditions.

We matched each condition with a graph.

This was the four steps we came up for an engine.

We calculate the U, Q, and W for a complete cycle.

This was another problem we did for a complete cycle.

week 4 day 2

We started electric forces.

We did some tape experiment. Maybe it was a wet day, it didn't go well.

But at least, the tapes attract each other.

Then we looked at a metal ball repel another metal ball that hangs under a string. We calculated the force on the repeled ball in terms of mass, displacement and length of the string.

We inserted points and got this graph of the force/seperation distance.

We then looked into electrical force between two point particles that have charge.

Then we calculated electrical force in two dimension.

this is a electric generator. charge went to the paper strips. when they have same charge, they repel each other.

Then we did calculation of electric force based on the formula Fe=Kq1q2/r^2

comparing to gravitation formula Fg=Gm1m2/r^2

Then we noticed gravitation force is very small.

Week 4 day 1

Today, we looked at work output through temperature.

COP is coefficent of performance.

For heating, COP=Qh/W

For cooling, COP=Qc/W

As maximum, COP=Th/(Th-Tc)

Efficiency=W/Qh

Then we did this problem.

This is the solution.

Week 3 day 2

Today, we are still on thermodynamics.

In the picture above, it's a device that transfer thermal energy into electrical energy. When the two side metal touches two reservoir that has a difference in temperature, the middle plate will spin.

Through this device, we can measure the eletricity generated through this device by the difference in temperature.

Then we got into some heat capacity. Cp=Cv+R. while this is hold true, Cv changes based on the type of gas. For monotomic gases, Cv=3/2R. For diatomic gases, Cv=5/2R. while R is a constant that equals 8.314.

These two pictures are from Work formula for adiabatic process meaning heat is held constant.

then we did this cycle. we could calculate the work and change in internal energy, then we can calculate heat.

This is otto cycle model.

Week 2 Day 2

Today we did some labs that the pressure is constant while the temperature and volume changes.

The piston is free to move. thus the pressure inside is equal to surrounding pressure. Then, as we put the flask into hot water, the volume will increase.

We can use w=p*\delta V for constant pressure. We did this thermal expansion problem from the picture above.

We also consider the kinetic energy of molecules inside the container. The final formula was shown in the picture above.

Base on the formula before, we can calculate the relationship between percent change in T and V.

Lastly, we did a problem that uses the formula we got today as above.

week 2 day 1

This day, we were still on thermal dynamics. We focused on the same gas but different conditions in terms of pressure, volume, and temperature.

The first little lab was that heating up a can with half filled with water, then put the can into cold water facing down. The can squized. when the can was heat up, the water molecules take more space. but when its put into  cold water, temperature dramaticly decreases. PV have to decrease too based on p1v1/t1=p2v2/t2.

Then we heated up the can with only air inside. then we put it into cold water facing down. the can didnt change shape, but it sucked up some water into the can. When the can was put into cold water after being heated, the sudden decrease in temperature caused the volume of gas decrease, so it sucked up some water to fill the space.

Then we looked into the relationship between pressure and volume. The graph above shows everything.

Then we looked into the relationship between the pressure and temperature.

We worked on this problem.

Solution to this problem was above.

We did a lab about pressure.

we evacuate the air inside the tank. we noticed the balloon gets bigger.

because the amount of air inside the balloon was constant. when the outside pressure decreases, air inside the balloon trys to go out to balance the pressure.

Physics 4B Week 1 Day 2

We were covering thermal expansion on this day

There were a metal ball attached with a handle and a ring that has smaller radius than the ball too.

Obviously the ball cannot pass through the ring at room temperature. We made some guesses on what will happen after both ring and the ball were heat up.

It's kind of like common sense that when you heat something up, it will expand. We made similar guess. And we were right.

We took it into more depth than just some observation and common sense. We did the formula about thermal expansion as above.

We also did and experiment on the linear expansion of this long and thin piece of medal "staff"

We heat it up, and expect the length will increase a little.

We also made the calculations based on equation.

However the result didn't really match the actual value.

Then we notice the uncertainty of this experiment.

we assumed the original length to be 1m when it's probably not exactly 1 m, it has an uncertainty of 0.1 m. the initial temperature was anounced by the professor which has no back up but only random guesses. Due to these bad habits of experimenting, our result was off. And it should been off.

Then we did an experiment of heating water.

We calculate the energy put in by multiply the power of the heater by the time.

Then based on q=mc\delta T, we can figure out the change in temperature from loggerpro.

We knew heat capacity of water is 4.18J/mol*C, then we calculated the mass of the water.

Then prof. mason randomly spill a lot of water on other students' table, and assume those water was boiled away. 

We looked into the idea of latent heat which is the energy required to change phase on one gram of water.

Through the calculation, we figured out how much water was boiled away based on the amount of heat put in.

Then we did this pressure in a tube lab.

It was really fun to see Isai blow the water out of the tube.

We didn't take this part in our data. It was just fun to watch, thus I uploaded it.

Calculations were above. We figured out the pressure Isai blow. Good thing is that we don't need to know the crosssection area of the tube. The A cancels out in the calculation.

It was the second day of physics 4b. things got better. We got into habits of taking photoes of the white boards as our notes.