Potential And Kinetic Energy.docx

Potential and Kinetic Energy According to the dictionary, energy is the strength and vitality required for sustained physical or mental activity. While in a book published by Phoenix publishing house, energy is a power derived from the utilization of physical or chemical resources, especially to provide light and heat or to work machines. There are two main types of energy which is the kinetic energy and potential energy. Kinetic energy is the energy on motion. Any object that has motion is kinetic energy. The following equation is used to represent the kinetic energy (KE) of an object. KE = (1/2)mv2 where m = mass of object v = speed of object Kinetic energy is a scalar quantity because it has no direction. The kinetic energy of an object is completely described by magnitude alone. The standard metric unit of measurement for kinetic energy is the Joule. 1 Joule is equivalent to 1 kg*(m/s)^2. Examples (from physicsclssroom.com): 1. Determine the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18.3 m/s. KE = 0.5*m*v2 KE = (0.5) * (625 kg) * (18.3 m/s)2 KE = 1.05 x105 Joules

2. If the roller coaster car in the above problem were moving with twice the speed, then what would be its new kinetic energy? If the speed is doubled, then the KE is quadrupled. Thus, KE = 4 * (1.04653 x 105 J) = 4.19 x 105 Joules. or KE = 0.5*m*v2 KE = 0.5*625 kg*(36.6 m/s)2 KE = 4.19 x 105 Joules Another type of energy is the potential energy. Potential energy is a result of gravity pulling downwards. The gravitational constant, g, is the acceleration of an object due to gravity. This acceleration is about 9.8 meters per second on earth. Electric Company Potential Kinetics (from classrooms.synonyms.com) The electricity that fuels our homes is supplied by potential energy turned kinetic, either in the form of an electric plant fueled by coal, a hydroelectric dam, or other source such as solar cells. The coal is stored potential energy at its most inert; it must be burned to translate itself into kinetic energy. The water behind the dam is, despite its eddies and currents, relatively inert as well, but it also supplies power when it is transformed by flowing through the dam and transferring it kinetic energy. Switch on the light. The switch's movement releases potential energy, while the light is kinetic. Gravitational potential energy is the energy stored in an object as the result of its vertical position or height. Its equation is: GPE = mass * g * height GPE = m*g*h

Where "g" is the standard acceleration of gravity which equals 9.8 m/s2. The height is determined based on the height the object could potentially fall. The height may be the distance above the ground or perhaps the lab table we are working on.

Example: What is the potential energy of a 2 kg rock sitting at the top of a 10 meter high cliff? GPE = mass * g * height GPE = 2kg * 9.8 m/s2 * 10m GPE = 196 J Elastic potential energy is the energy stored in elastic materials as the result of their stretching or compressing. Elastic potential energy can be stored in rubber bands, bungee chords, trampolines, springs, an arrow drawn into a bow, etc.

A force is required to compress a spring; the more compression there is, the more force that is required to compress it further. For certain springs, the amount of force is directly proportional to the amount of stretch or compression (x); the constant of proportionality is known as the spring constant (k). Fspring = k • x The equation is PEspring = 0.5 • k • x2 where k = spring constant x = amount of compression (relative to equilibrium position)

Falling and Bouncing Balls (from classrooms.synonyms.co) One of the best—and most frequently used—illustrations of potential and kinetic energy involves standing at the top of a building, holding a baseball over the side. Naturally, this is not an experiment to perform in real life. Due to its relatively small mass, a falling baseball does not have a great amount of kinetic energy, yet in the real world, a variety of other conditions (among them inertia, the tendency of an object to maintain its state of motion) conspire to make a hit on the head with a baseball potentially quite serious. If dropped from a great enough height, it could be fatal. When one holds the baseball over the side of the building, potential energy is at a peak, but once the ball is released, potential energy begins to decrease in favor of kinetic energy. The relationship between these, in fact, is inverse: as the value of one decreases, that of the other increases in exact proportion. The ball will only fall to the point where its potential energy becomes 0, the same amount of kinetic energy it possessed before it was dropped. At the same point, kinetic energy will have reached maximum value, and will be equal to the potential energy the ball possessed at the beginning. Thus the sum of kinetic energy and potential energy remains constant, reflecting the conservation of energy, a subject discussed below. It is relatively easy to understand how the ball acquires kinetic energy in its fall, but potential energy is somewhat more challenging to comprehend. The ball does not really "possess" the potential energy: potential energy resides within an entire system comprised by the ball, the space through which it falls, and the Earth. There is thus no "magic" in the reciprocal relationship between potential and kinetic energy: both are part of a single system, which can be envisioned by means of an analogy. Imagine that one has a 20-dollar bill, then buys a pack of gum. Now one has, say, $19.20. The positive value of dollars has decreased by $0.80, but now one has increased "non-dollars" or "anti-dollars" by the same amount. After buying lunch, one might be down to $12.00, meaning that "antidollars" are now up to $8.00. The same will continue until the entire $20.00 has been spent. Obviously, there is nothing magical about this: the 20dollar bill was a closed system, just like the one that included the ball and

the ground. And just as potential energy decreased while kinetic energy increased, so "non-dollars" increased while dollars decreased.