Law of conservation of energy

This law states no energy is ever lost and can only be transferred from one state to another.

9 types of energy

Chemical: Energy stored in molecular bonding between atoms
Nuclear: Energy stored in the atom
Kinetic: energy in the form of a motion
Gravitational potential: potential energy generated from an object falling due to gravity
Elastic: Energy stored in an object that is stretched out of its natural state
Thermal: Energy as heat
Sound: Energy that exists as pressure of an substance
Electromagnetic: Energy in light, including the ones that we can’t see
Electrical: Energy of difference between negative and positive charges

How do these energies relate to each other (A few examples)

Chemical to kinematic, thermal and electrical: In our body, chemical reaction is a constant. The food we eat is converted into kinematic energy for us to move, thermal energy to keep our body at a stable temperature and electrical energy for the brain to send signals.

Nuclear to thermal and electromagnetic: Nuclear energy powers the sun, converting to thermal energy that makes it so hot and electromagnetic energy as light shining down on Earth.

Kinetic and gravitational potential: When we throw a ball up in the air, it slows down as the energy converts to gravitational potential energy and speeds up as it falls down converting back into kinetic energy.

Elastic and kinetic: Stretching a rubber band stores kinetic energy within the band and when your hand is released it is converted back to kinetic energy and the rubber band bounces away from your hand.

Sound and kinetic: if hum as you put your hands on your throat, you can feel the vibration, which is what creates the sound.

Electrical to all except nuclear: We have electrical devices everywhere, flashlight converts electrical energy to light, speakers converts electrical energy into sound. Look around, see what else you can find!

Work, power and efficiency

work can be a confusing concept in physics. It is how much energy is spent in the movement of an object from 2 point in time. Power is how much work is done in each second. Efficiency is how much is done vs how much energy is put in, the more efficiency something is, the more of energy is converted for a useful cause and less is wasted.

Practice question

Nuclear power is one of the options for the future energy source. Some perceives it as efficient, some perceives it as dangerous. Regardless of either, this technology relies heavily on physics, specifically in transformation and transference of energy.

Nuclear power is the power within an atom, it is vast and is incomparable with the chemical energy that we are so familiar with. Because of how immense this energy is, there is a set of processes in converting nuclear energy to electrical energy safely and effectively through an nuclear power plant. First atoms are broken apart and the nuclear energy is released as thermal, light and sound energy. Through radiation of light and conduction with water these energies are either wasted or converted entirely to thermal energy into water. Water boils and vaporizes, through convection it moves away from the heat source and travels in an organized manner through designated route turning turbines in the process. The kinetic energy of turbine is then converted into electrical energy through special mechanisms and is send through cables supplying electricity for millions of family.

With this technology, we can improve our efficiency in generating energy as 1 kg of nuclear power fuel is equivalent of 14,000 kg of coals. This reduces our carbon footprint and the price of electricity, making generating energy a quicker and easier process that requires less personnel.

However, nuclear energy is still a developing technology, even within this field there are far more efficient way of generating energy. The way I described to you was called nuclear fission, the counterpart to it is called nuclear fusion, which is what powers the sun. With the advancement of technology, nuclear energy will continue to improve in both efficiency and safety, as it is one of the potential future energy source that we look forward to.

Work cited:

https://www.euronuclear.org/info/encyclopedia/f/fuelcomparison.htm

Today, we run experiments on pressure’s effects on change of forms.

In the bottle, a less pressurized environment is formed, which allows the water to break free from its bonding much more easily, causing it to become vapors. The same thing applies for places in higher latitude, with less air weighing down, the temperature at which form change take place is lower.

Today, I did a few questions on transfer of thermal energy. One of the questions was about the transfer between water and a type of metal. Given mass, temperature and specific heat capacity of both substances, the question asked for the temperature of metal of and water when they are equal.

When I first approach this question, I found the total energy of water and metal first, then divided it to find the final temperature, which totals to 3 equations.

Today, I learned to arrange the equation using the change in energy instead of the total to final approach:
Q1 = Q2
Q1 – Q2 = 0
m1c1(initial T1 – final T) – m2c2(initial T2 – final T) = 0

This approach is cleaner and only need 1 equation, leaving less chance for mistakes.

Today I worked on the energy worksheet and learned how to draw a LOL diagram.

LOL diagram shows the change in energy of a system between 2 moments in time.

The left bar graph shows the energy of the first moment, the right bar graph shows the energy in the final moment and the middle shows in the flow of energy.

In this diagram we see the Eg flowing in, which is reflected on the right chart as the increase in eg.

The LOL diagram is unable to show where the energy is flowing to and where the energy comes from, so it is just a way to display the flow in of energy in and out of a system on paper.

Today I learned an object must take in energy to change from solid to liquid or gas and releases the same amount of energy when worked the other way around.

We can see some parts of the graph have a positive slope and other parts have zero, which is a flat horizontal line.

The change in state from one of stronger bonding to one of less requires a lot of energy, as shown by the area under the flat lines. This need in energy is called “latent heat” and differs depending on the which form change is taking place and the substance under going it.

Change in temperature

We also learned a new formula, Q = mcΔT.
Q: Total thermal energy
m: mass
c: heat capacity
ΔT: change in temperature

This formula is used when any 3 of the 4 components of the formula are given.

Latent heat

The formula for change in state is Q = mLf or Q = mLv, depending on which form change is taking place.
Q: Total thermal energy
m: mass
Lf: Latent heat of fusion (used for solid – liquid form change)
Lv: Latent heat of vaporization (used for liquid – gas form change)

Today in groups of two, we are doing the experiment of rolling marbles down the pipe ourselves and are recording the initial height and final speed of the marble at the end of the pipe.

We recorded the data with 5 different heights for 5 trials each and calculated the average and the uncertainty.

Today we talked about the conversion between kinetic, gravitational potential and thermal energies in a closed system.

When the friction is set to zero, the energy is converted between gravitational potential energy and kinetic energy without any change in thermal energy. However, as the friction increases, the more energy is converted to thermal and the mass of the person. But mass also increases the total energy in the system.

The interesting thing is, when friction is ignored, the person goes all the way to the other side at the same height and will slide back and forth indefinitely.

We did clicker exercise today, which is a digital quiz that is projected onto the white board. We answer it individually and discuss our choice. The focus today is on the conversion of gravitational potential energy and kinematic energy.

The questions today are based on the rolling speed of marbles in pipes of different length while the initial gravitational potential energy are the same. The difference is in the slope that the pipes make, below is a video on situation in real life. The right pipe is the longer one and the left is shorter, marbles of the same size are rolling down at the same time.

As you can see, the marble from the shorter pipe hits the ruler first. This is because the shorter pipe has a steeper slope, so the gravitational potential energy is converted into kinematic energy quicker, therefore the marble in that pipe reached the maximum velocity first and rolled to the ruler first. 

The next experiment is run with the same 2 pipes but one of the marbles is changed to one of 3 times the mass. The result made no difference. We know that the gravitational potential energy is greater with object of greater mass. That means the larger marble should have triple the gravitational potential energy. However, it also takes triple the energy to make the marble to move the same amount, so the mass made no difference to the result. On another note, had the co-efficient of friction for the table or pipe been greater, the mass would indeed make a difference, must in the experiment where the friction is neglect-able, it is not considered.

Today we spent great deal of time learning about work and energy.

Gaining and losing of energy in a system:

Two ways of calculating work:

This method is significantly more complicated, but is able to find the value of work in perspectives of each force that was applied to the object. I think net force is the only useful thing though, so it’s pointless to find multiple different values for work.

The right side is not going to be too useful, since there is too many conditions involved, but the left side is short and sweet, I find it rather helpful and easy to remember.