Kinetic Energy

Kinetic Energy Kinetic energy is the energy of motion. An object that has motion - whether it is vertical or horizontal motion - has kinetic energy. There are many forms of kinetic energy - vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another). To keep matters simple, we will focus upon translational kinetic energy. The amount of translational kinetic energy (from here on, the phrase kinetic energy will refer to translational kinetic energy) that an object has depends upon two variables: the mass (m) of the object and the speed (v) of the object. The following equation is used to represent the kinetic energy (KE) of an object. KE = 0.5 • m • v2 where m = mass of object v = speed of object This equation reveals that the kinetic energy of an object is directly proportional to the square of its speed. That means that for a twofold increase in speed, the kinetic energy will increase by a factor of four. For a threefold increase in speed, the kinetic energy will increase by a factor of nine. And for a fourfold increase in speed, the kinetic energy will increase by a factor of sixteen. The kinetic energy is dependent upon the square of the speed. As it is often said, an equation is not merely a recipe for algebraic problem solving, but also a guide to thinking about the relationship between quantities. Kinetic energy is a scalar quantity; it does not have a direction. Unlike velocity, acceleration,force, and momentum, the kinetic energy of an object is completely described by magnitude alone. Like work and potential energy, the standard metric unit of measurement for kinetic energy is the Joule. As might be implied by the above equation, 1 Joule is equivalent to 1 kg*(m/s)^2. 1 Joule = 1 kg • m2/s2      Electricity is a force caused by electric charge. It is a form of energy which we use to power machines and electrical devices. When the charges are not moving, electricity is called static electricity. When the charges are moving they are an electric current, sometimes called dynamic electricity. Lightning is the most obvious kind of electricity in nature but sometimes static electricity causes things to stick together. Static electricity occurs when the number of electrons of atoms in a material are either more than usual or less than usual. If the electrons stay where they are, the atom that has too many or too few electrons will attract or sometimes repel other atoms. If the electrons move from where there are too many to where there are too few, a flow of electrons will occur, an electrical current. Scientists have found we can make electricity if we pass a magnet close to a metal wire, or if we put the right chemicals in a jar with two different kinds of metal rods. We can also make static electricity by rubbing two things, for instance a wool cap and a plastic ruler, together. This may make a spark. Scientists have observed that electricity can flow like water from one place to another, either as a spark or as a current in a metal. They now know that all matter has an electric charge, but this is mostly cancelled out by the presence of matter with an opposite charge. We only see an effect when there is too much or too little electric charge in one place so that it is not cancelled out. Since the nineteenth century, electricity has been used in every part of our lives. Until then, it was just a curiosity or a force of nature seen in a thunderstorm. People make most our electric energy in generators. The biggest generators are in power stations. Some of our electricity comes from photovoltaic cells or from batteries. Electricity arrives at our homes through wires from the places where it is made. It is used by electric lamps for producing light, electric heaters to produce heat, etc. It is also used by many devices such as washing machines, electric cookers, etc. for doing work. In factories, electricity is used for running machines and computers. The people who deal with electricity and electrical devices in our homes and factories are called "electricians". RADIOACTIVE DECAY Radioactive decay, also known as nuclear decay or radioactivity, is the process by which a nucleus of an unstable atom loses energy by emitting ionizing radiation. A material that spontaneously emits this kind of radiation — which includes the emission of alpha particles, beta particles, gamma rays and conversion electrons — is considered radioactive. Radioactive decay is a stochastic (i.e. random) process at the level of single atoms, in that, according to quantum theory, it is impossible to predict when a particular atom will decay.[1] However, the chance that a given atom will decay never changes, that is, it does not matter how long the atom has existed. For a large number of atoms however, the decay rate for the collection can be calculated from the measured decay constants, and the half-lives of the nuclides calculated. These numbers have no known limits for shortness or length of duration, and range over 55 orders of magnitude in time. There are many types of radioactive decay (see table below). A decay, or loss of energy, results when an atom with one type of nucleus, called the parent radionuclide (or parent radioisotope[note 1]), transforms into an atom with a nucleus in a different state, or with a nucleus containing a different number of protons and neutrons. The product is called the daughter nuclide. In some decays, the parent and the daughter nuclides are different chemical elements, and thus the decay process results in the creation of an atom of a different element. This is known as a nuclear transmutation. The first decay processes to be discovered were alpha decay, beta decay, and gamma decay. Alpha decay occurs when the nucleus ejects an alpha particle (helium nucleus). This is the most common process of emitting nucleons, but in rarer types of decays, nuclei can eject protons, or specific nuclei of other elements in a process called cluster decay. Beta decay occurs when the nucleus emits an electron or positron and a neutrino, in a process that changes a proton to a neutron or the other way about. The nucleus may capture an orbiting electron, causing a proton to convert into a neutron in a process called electron capture. All of these processes result in a nuclear transmutation.  SOUND AND WAVES Sound is transmitted through gases, plasma, and liquids as longitudinal waves, also called compression waves. It requires a medium to propagate. Through solids, however, it can be transmitted as both longitudinal waves and transverse waves. Longitudinal sound waves are waves of alternating pressure deviations from the equilibrium pressure, causing local regions of compression andrarefaction, while transverse waves (in solids) are waves of alternating shear stress at right angle to the direction of propagation. Sound waves may be "viewed" using parabolic mirrors and objects that produce sound.[5] The energy carried by an oscillating sound wave converts back and forth between the potential energy of the extra compression (in case of longitudinal waves) or lateral displacement strain (in case of transverse waves) of the matter, and the kinetic energy of the displacement velocity of particles of the medium. Sound wave properties and characteristics Sinusoidal waves of various frequencies; the bottom waves have higher frequencies than those above. The horizontal axis represents time. Sound waves are often simplified to a description in terms of sinusoidal plane waves, which are characterized by these generic properties:  Frequency, or its inverse, the period Wavelength Wave number Amplitude Sound pressure Sound intensity Speed of sound Direction Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at standard temperature and pressure, the corresponding wavelengths of sound waves range from 17 m to 17 mm. Sometimes speed and direction are combined as a velocity vector; wave number and direction are combined as a wave vector. Transverse waves, also known as shear waves, have the additional property, polarization, and are not a characteristic of sound waves.