Work

1. Work • Work is the result of a force applied times the distance traveled in the direction of the applied force. • Any movement not in the direction of the applied force is disregarded. • W = Fd • Work is measured in joules.

2. Potential Energy Potential energy can be thought of as energy stored within a physical system. It is called potential energy because it has the potential to be converted into other forms of energy, such as kinetic energy, and to do work in the process. The standard (SI) unit of measure for potential energy is the joule, the same as for work, or energy in general. The term "potential energy" was coined by the 19th century Scottish engineer and physicist William Rankine.

3. Gravitational potential energy • PE = mgh • The factors that affect an object's gravitational potential energy are its height relative to some reference point, its mass, and the strength of the gravitational field it is in. • Thus, a book lying on a table has less gravitational potential energy than the same book on top of a taller cupboard, and less gravitational potential energy than a heavier book lying on the same table. • An object at a certain height above the Moon's surface has less gravitational potential energy than at the same height on Earth because the Moon's gravity is weaker. The gravitational force keeps the planets in orbit about the Sun.

4. Elastic potential energy • Elastic potential energy is the potential energy of an elastic object (for example a bow or a catapult) that is deformed under tension or compression. • A spring has potential energy when it is compressed or stretched. PEs = ½ kx2

5. Chemical potential energy • Chemical potential energy is a form of potential energy related to the structural arrangement of atoms or molecules. This arrangement may be the result of chemical bonds within a molecule or otherwise.

6. Electrical potential energy • The electrostatic potential energy is the energy of an electrically charged particle (at rest) in an electric field. It is defined as the work that must be done to move it from an infinite distance away to its present location, in the absence of any non-electrical forces on the object. This energy is non-zero if there is another electrically charged object nearby. Strong (sparks) in gas inside a plasma lamp

7. Electrodynamic potential energy • In case a charged object or its constituent charged particles are not at rest, it generates a magnetic field giving rise to yet another form of potential energy, often termed as magnetic potential energy. This kind of potential energy is a result of the phenomenon magnetism, whereby an object that is magnetic has the potential to move other similar objects. Magnetic objects are said to have some magnetic moment. Magnetic fields and their effects are best studied under electrodynamics.

8. Nuclear potential energy • Nuclear potential energy is the potential energy of the particles inside an atomic nucleus, some of which are indeed electrically charged. This kind of potential energy is different from the previous two kinds of electrical potential energies because in this case the charged particles are extremely close to each other. The nuclear particles are bound together not because of the coulombic force but due to strong nuclear force that binds nuclear particles more strongly and closely. Weak nuclear forces provide the potential energy for certain kinds of radioactive decay, such as beta decay.

9. Thermal potential energy • The thermal energy of an object is simply the sum of the kinetic energies of the particles constituting it (which are in random motion) plus the potential energies of their displacements from their equilibrium positions as they oscillate or move around them. In the case of an ideal gas, there is no potential energy due to interactions of particles, but kinetic energy may include a rotational part too (for multiatomic gases) – if rotational levels are excited at a given temperature T. • Solar updraft towers use this kind of power.

10. Kinetic Energy • Kinetic Energy is called energy in motion. • KE = ½ mv2 • The faster the object moves its kinetic energy increases by the square. • KE is measured in joules.

11. Conservation of Energy • Energy can change from for to for without loss or gain. • For instance take the scenario of a girl shooting archery. • She applies work to pull back the bow. • The bow acquires PE. • The bow is released and the arrow acquires KE.

12. Power • How fast you do work is called power. • Power = Work divided by time. • P = W / Δt • Power is measured in Watts • So, watts = Joules/second • The fast you do something the more power is produced or used.

13. Hooke’s Law • F = kx • Hooke’s law states that as you place a force on a spring the spring will stretch (x) a certain distance depending on the spring constant (k) of the spring. • If the elastic limit is exceeded you will ruin the spring and its spring constant (k) will not conform appropriately.

14. Roller Coaster • The roller coaster is the perfect representation of conservation of energy. The first hill is always the highest point of the ride unless there is an apparatus to further lift the cars. As the roller coaster goes down the hill the PE is converted to KE. If you do not neglect friction then the work done by friction added to the KE will equal the PE at the top.