07.04.2019: Science Notebook Ch. 13

Today’s soundtrack is George Gershwin: Rhapsody in Blue, a thrilling orchestral arrangement. The first track, “Strike Up the Band,” would be the perfect score for the most epic swordfight in history.


Everything You Need to Ace Science in One Big Fat Notebook
Chapter 13: Forms of Energy

We’re in the first chapter of the fourth unit, “Energy.” Today we will be learning about the different forms and properties of energy.

We’ve already learned that matter is always conserved. Energy is the same. The amount of energy present in the universe is (and always will be) the same. The Law of Conservation of Energy tells us that “energy can neither be created nor destroyed” (p. 130); it can only “change forms and be transferred between objects” (p. 130).

When an object is in motion or is in a position to be moved, the object possesses mechanical energy, of which there are two kinds: potential energy and kinetic energy. The former is possessed by an object that could move (for example, a book on a shelf); the latter is possessed by an object in motion (the same book falling off the shelf). What if an object in motion collides with another object? The Law of Conservation of Energy holds true; the kinetic energy of the first object is transferred to the second; the first object decelerates, and, assuming the mass of the second object is low enough (and that both the velocity and mass of the first object are high enough), the second object will take on kinetic energy and start to move.

So we can see that the higher the book on the shelf is, the more potential energy it has, since it can build more velocity before hitting the ground, and will therefore have more kinetic energy to transfer to another object upon impact.

Some scientists say that there are only those two kinds of energy (kinetic and potential); others classify further, saying that there are five kinds of kinetic energy and four kinds of potential energy:

  1. Kinetic Energies
    1. Mechanical Kinetic Energy
      1. Moving objects
    2. Thermal Energy
      1. Vibrating molecules that affect temperature
    3. Electromagnetic Energy
      1. Light waves (both visible and invisible)
    4. Sound Energy
      1. Molecules bumping into each other to transmit sound
    5. Electric Energy
      1. The flow of electrons
    6. Nuclear Fission
      1. Energy released through splitting of atoms
  2. Potential Energies
    1. Gravitational Potential Energy (or Mechanical Potential Energy)
      1. Stored in the height of an object
    2. Elastic Energy
      1. Stored in the compression or stretching of elastic materials
    3. Nuclear Energy
      1. Stored in the nucleus of radioactive atoms
    4. Chemical Energy
      1. The energy stored in chemical bonds
        – (p. 133)

Summary:

  1. “Conservation of Energy” says that energy can never be created or destroyed, as the amount of energy in a system remains constant.
  2. Potential energy is stored energy.
  3. Kinetic energy is the energy of an object based on its motion.
  4. When a cow eats grass, it digests and breaks chemical bonds in the grass to release thermal and kinetic energy.
  5. Chemical energy is a potential energy: it bonded chemicals that, when the bond is broken, will release energy.
  6. The two factors affecting the amount of an object’s potential energy include height and mass.
  7. Energy is constantly changing from one form to another.
  8. If a car hits another car, causing the second car to lurch forward, kinetic energy was transferred.

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