The Physics of Energy: Chapter 1

Conservation of Energy: - energy is never lost, only converted - energy does not change with time - when people say energy has been consumed, they mean it’s been degraded to a less useful state

Matter = Energy - matter is a form of energy - mass contains energy but it’s impossible to extract and use with any foreseeable technology

I wonder if there’s a way to directly convert mass to energy without using antimatter? We could harness all the mass energy on Earth. Or even if we could somehow create antimatter.

• textbook said that if we wanted to convert x kg of pulley trucks we would need x kg of pulley truck antimatter

Units

Fundamental Unit of Energy: 1 Joule = \(1 kgm^2/s^2\)

Unit of Force: Newtons 1 Newton = \(1kg m/s^2\)

Work: Multiplying force along a distance.

Power: Rate at which energy is used, measured in watts 1 W = 1 J/s

KwH: 1KwH = 1KW x 36000s = 3.6MJ

Pressure \[P = F/A = m/d \cdot t^2\] Unit: Pascals (Pa) \[1 Pa = 1 N/m^2\]

Forms of Energy

Each form of energy can be converted into every other form of energy.

Mechanical and Kinetic Energy - KE of an object of mass m moving at speed v \[KE = \frac{1}{2}mv^2\]

Thermal Energy - Contained in the microscopic dynamics of a large number of molecules, atoms or other constituents - The thermal energy of air would include KE + energy of the vibrations in the air

Electromagnetic Energy - one of the four fundamental forces of nature - Electrically charged particles produce electric and magnetic fields that exert forces on other charged particles

Chemical Energy - energy stored in chemical energy bonds within a material - e.g the chemical energy stored in the carbon bonds in an apple is released when someone can eat it and then can walk - energy in a chemical bond can be measured in electron volts (eV) - 1eV is the energy needed to move a single electron across a one volt electric potential difference \[1ev = 1.602 18 x 10^{-18}\] - standard unit of energy is the calories (Cal)

Nuclear binding energy - short range force that binds the nucleons in a nuclei together

Mass Energy - mass is a form of energy - each particle is an excitation of a quantum field e.g single photon is an excitation of electromagnetic field - its difficult to convert mass energy into a useful form - can be done by using an antiparticle to annihilate the particle and release if the mass energy as electromagnetic radiation and/or kinetic energy - antimatter is not found naturally in the solar system \[E=mc^2\]

Final Thoughts:

Energy is everywhere - it’s matter of converting it into useable forms efficiently. Kardasheve Scale measures types of civilizations by our ability to extract energy from different sources. –> Civilization 1: can harness all energy on earth given by our planet star. Read more here