Energy in my own words can be defined as the ability to do work or activity when a chemical reaction takes place energy in various forms may be either emitted or absorbed. It is everything around; us. We can hear energy as a sound, we can see it as light, we can fell it in the wind. We can use energy when you hit a tennis ball, compress a spring, lifting a grocery bag. The energy continually shaping and reshaping. The earth and maintaining all the life that exists on it. The two states of energy are kinetic energy and potential energy and they are different in many ways.
Potential energy is energy of shape or position and stored.
Kinetic energy is energy that a moving object has due to its motion which is also energy of motion. If an object or organism does work (exerts a force over a distance to move an object), the object or organism uses energy. You use energy when you swim in a race. Electric charges in a current. use energy as they move along a wire. A car uses energy to carry passengers from one place to another. Because of’ the direct connection between work and energy, energy is measured in the same unit as work. Energy is measured in joules (J).
In addition to using energy to do work, objects can gain energy because work is being done on them. If work is done on an object, energy is given to the object. When you kick a football, ‘You give some of your energy to the football to make it move. When you throw a bowling ball, you give it energy. When that bowling ball hits the pins, it loses some of its energy to the pins, causing them to fall down.
FORMS OF ENERGY
Energy appears in many forms. The five main forms of energy are mechanical, heat, chemical, electromagnetic, and nuclear. It may surprise you to learn that your body is an an “energy factory” that stores and converts various forms of energy. After reading about each form of energy, see if you can describe how your energy factory works.
MECHANICAL ENERGY: Matter that is in motion has energy. The energy associated with motion is called mechanical energy. Water in a waterfall has a great amount of mechanical energy. So does wind. An automobile traveling at 95 km/hr has mechanical energy. A jet plane cruising at 700 krn/hr has even more! When you walk, ride a bike, or hit a ball, you use mechanical energy. Sound is a type of mechanical energy. Even the blood flowing through your blood vessels has mechanical energy.
HEAT ENERGY: All matter is made up of tiny particles called atoms that are constantly moving. The internal motion of the atoms is called heat energy. The faster the particles move, the more beat energy is produced. Rub your hands together for several.
Did you feel heat? Using the friction between your hands, you converted mechanical energy (energy of motion) into heat energy! Heat energy usually results from friction. Heat energy causes changes in the temperature and phase (solid, liquid, gas) of any form of matter. For example, it is heat energy that causes your ice cream cone to melt and drip down your hand.
CHEMICAL ENERGY: Energy exists in the bonds that hold atoms together. This energy is called chemical energy. Often, when bonds are broken, this chemical energy is released. The fuel in a rocket engine has stored chemical energy. When the fuel is burned, chemical energy is released and converted into heat energy. When you start a fire in a charcoal grill, you are releasing chemical energy. When you digest food, bonds are broken to release energy for your body to store and use. When you play field hockey or lacrosse, you are using the chemical energy stored in your muscles that you obtained from food.
ELECTROMAGNETIC ENERGY: Moving electric charges have the ability to do work because they have electromagnetic energy. Power lines carry electromagnetic energy into your home in the form of electricity. Electric motors are driven by electromagnetic energy. Light is mother form of electromagnetic energy. Each color of light-red, orange, yellow, green, blue, violet-represents a different amount of electromagnetic energy. Electromagnetic energy is also carried by X-rays, radio waves, and laser light.
NUCLEAR ENERGY: The nucleus, or center, of an atom is the source of nuclear energy. When the nucleus splits, nuclear energy is released in the form of heat energy and light energy. Nuclear energy is also released when lightweight nuclei collide at high speeds and fuse (join). The sun’s energy is produced from a nuclear fusion reaction in which hydrogen nuclei fuse to form helium nuclei. Nuclear energy is the most concentrated form of energy.
Light, whether seen as a beautiful rainbow or used as laser beams, is an important part of everyday life. No matter how it is used, light is a form of energy.
Kinetic and Potential Energy
Stretch a rubber band between your thumb and index finger. Keep the rubber band stretched without any motion. How long can you hold it this way? After a short while, as your fingers begin to tire, you become aware of the energy in the rubber band. Yet the rubber band is not moving! This is because the energy of the stretched rubber band is stored in it, Remember that energy is the ability to do work. Release your thumb and the rubber band moves. As the rubber band moves back to its normal shape, it does work.
The energy that you felt when you stretched the rubber band was different from the energy displayed when the rubber band snapped back to its original shape. They are two different states of energy. The five different forms of energy you just learned about can be classified into either one of these states of energy. The two states of energy are called kinetic energy and potential energy.
An object that is moving can (to work on another object by colliding with that object and moving it through a distance. A flying rubber band does work when it flattens a house of cards, A swinging hammer (does work on a nail as it drives the nail into a piece of wood. A wrecking ball (does work as it knocks down a wall. Because an object in motion has the ability to (to work, it has energy. The energy of motion is called kinetic energy. The word kinetic comes from the Greek word (kinetikos) which means motion.” Why do the particles in matter have kinetic energy?
Suppose you are accidentally hit with a tennis ball that has been tossed lightly toward you. It probably does not hurt you. Now suppose you are hit with the same tennis ball traveling at a much greater speed. You can certainly feel the difference! The faster an object moves, the more kinetic energy it has. So kinetic energy is directly related to the velocity of an object. You have more kinetic energy when you run than when you walk. In baseball, a fast ball has more kinetic energy than a slow curve. When does a skier have more kinetic energy, when skiing downhill or cross-country?
Do all objects with the same velocity have the same, kinetic energy? Think about the tennis ball again. Suppose this time it rolls across the tennis court and hits you in the foot. Compare this with getting hit in the fool, by a bowling ball traveling at the same speed as the tennis ball, The bowling ball is much more noticeable because the bowling ball has more kinetic energy than the tennis ball. A battleship moving at 40 km/hr has much more kinetic energy than a mosquito moving at the same. velocity, So kinetic energy must depend on something other than just velocity. The battleship has more kinetic energy because it has greater mass. Kinetic energy depends on both mass and velocity. The mathematical relationship between kinetic energy (K.E.), mass, and velocity is: According to this equation, an increase in either mass or velocity will mean an increase in kinetic energy. Which of these two factors, mass or velocity, will have a greater effect on kinetic energy? Why?
Now suppose you want to push a heavy box across the floor, You must exert a force on the box to move it. Thus you do work on the box. Before you moved the box, it did not have kinetic energy because it did not have velocity. As you give it kinetic energy,
the box picks up velocity. The more work you do, the faster the box will move. When you increase the velocity of’ an object, you increase its kinetic energy. The change in the kinetic energy of the box is equal to the work you have done on it.
You just read that some objects are able to do work as a result of their motion. Other objects can do work because of their position or shape. Potential energy is energy of position. A stretched rubber band has the potential, or ability, to fly across the room. A wound-up watch spring also has potential energy. It has the potential to move the hands of the watch around when it unwinds. An archer’s taut (tightly stretched) bow has the potential to send -an arrow gliding toward a target. A brick being held high above the ground has the potential to drive a stake into the ground when it falls onto it.
A car requires a longer distance in which to stop when traveling at faster velocities. Notice how quickly the distance increases for a small increase in velocity. A jack-in-the-box uses potential energy to burst out of its container How does the archer use potential energy?
Tightly wound springs store potential energy that can be used to turn the hands of time. What kind of potential energy does a pole vaulter have at the top of a vault?
Potential energy is related to work in a different way than kinetic energy is. Remember that a moving object has kinetic energy because it can do work as it moves. But an object with potential energy is not moving or doing work. Instead, it is storing the energy that was given to it when work was done on it. It has the ability, or potential, to give that energy back by doing work. The spring acquired potential energy because work was done on it by the person winding the watch. Work was done by the person who pulled back on the bow’s arrow. The brick acquired potential energy because work was done in lifting it.
Potential energy is not always mechanical, or associated with movement. For example, the chemical energy stored in food is an example of potential energy. The energy is released when the food is broken down in digestion and respiration. Similarly, fuels such as coal and oil store chemical potential energy. The energy is released when the fuel is burned. The nucleus of an atom consists of a number of particles held together by a strong force. The potential energy stored in the nucleus of an atom can be released if the nucleus is split in a nuclear reactor.
GRAVITATIONAL POTENTIAL ENERGY: Imagine that you are standing on the edge of a 1-meter diving board. Do you think you have any energy? You probably think you do not because you are not moving. It is true that you do not have kinetic energy. But you do have potential energy. Your potential energy is due to your position above the water.
If you stand on a 3-meter diving board, you have three times the potential energy you have on the 1-meter board. Potential energy that is dependent on height is called gravitational potential energy. A waterfall, suspension bridge, and falling snowflake all have gravitational potential energy. Weight also determines the amount of gravitational potential energy an object has. The old saying “The bigger they are, the harder they fall” is an observation of the effect of weight on gravitational potential energy. From your experiences, you may already know that gravitational potential energy is dependent on weight. You have a lot more gravitational potential energy with a heavy pack on your back than you do with a light pack.
The relationship between gravitational potential energy (G.P.E.), weight, and height can be expressed by the following formula:
G.P.E. = Weight X Height
You can see from this formula that the greater the weight, the greater the gravitational potential energy. The higher the position above a surface, the greater the gravitational potential energy.
This huge boulder in Arches National Park in Utah has a great deal of gravitational potential energy. So does a falling drop of water in a leaky faucet, The drop of water could not fall without the help of energy. Rock climbers, on the other hand, must do a tremendous amount of work to increase their gravitational potential energy.
When you think of useful energy, you may think of the energy involved in moving a car or the energy you get from the food you eat. But in both these examples, the useful energy was obtained by first converting energy from one form to another. The mechanical energy of the car came from burning the chemical energy of fuel. Your energy also comes from chemical energy-the chemical energy stored in the food you eat. Energy can be transferred from one object to another and energy can be changed from one form to another. Changes in the forms of energy are called energy conversions.
Kinetic-Potential Energy Conversions
One of the most common energy conversions involves the changing of potential energy to kinetic energy or kinetic energy to potential energy. A stone held high in the air has potential energy. As it falls, it loses potential energy because its height decreases. At the same time its kinetic energy increases because its velocity increases. Thus potential energy is converted into kinetic energy. Similarly, the potential energy stored in a bent bow can be converted into the kinetic energy of’ the arrow.
Conversions between kinetic energy and potential energy are taking place around you every day. Think of tossing a ball tip into the air, When you throw the ball up, you give it kinetic energy. As the ball rises, it slows down. As its velocity decreases, its kinetic energy is reduced. But at the same time its height above the Earth is increasing. Thus its potential energy is increasing. At the top of its path, the ball has slowed down to zero velocity so it has zero kinetic energy. All of its kinetic energy from the beginning of its flight has been converted to potential energy.
Then the ball begins to fall. As it gets closer to the Earth’s surface, its potential energy decreases. But it is speeding up at the same time. Thus its kinetic energy is increasing. When you catch it, it has its maximum velocity and kinetic energy, The potential energy of the ball has changed into kinetic energy. A continuous conversion between kinetic energy and potential energy takes place in a pendulum. Potential energy is greatest at the two highest points in the swing and zero at the bottom. Where is kinetic energy greatest?
Although conversions between kinetic energy and potential energy are common, they are not the only changes in energy that take place. All forms of energy can be converted to other forms. For example, the sun’s energy is not used merely as heat energy or light energy. It is converted to other forms of energy as well. Solar products convert the energy of sunlight directly into electricity. Green plants use the energy of the sun to trigger a process in which sugars and starches are made. These substances store the energy as chemical energy. In this process, electromagnetic energy is converted to chemical energy.
In an electric motor, electromagnetic energy is converted to mechanical energy. In a battery , chemical energy is converted to electromagnetic energy. The mechanical energy of a waterfall is converted to electromagnetic energy in a generator. Solar cells convert the sun’s energy directly into electrical energy. In a heat. engine (such as an automobile engine), fuel is burned to convert chemical energy into heat energy. The heat energy is then changed to mechanical energy. In a microphone-loudspeaker system, the microphone converts mechanical energy in the form of sound into electromagnetic energy in the form of electricity. The electromagnetic energy goes to the loudspeaker that then converts the electric signal back into sound.
A series of energy conversions is needed to produce the heat energy of the hair dryer. Trace the conversions.
- Donald Worster, (1993)”The Nature We Have Lost,” in The Wealthof Nature (New York: Oxford University Press.
- LynnWhite, “The Historical (1967) Roots of Our Ecologic Crisis, White thinks that “Since the roots of our trouble are so largely religious, the remedy must also be essentially religious, whether we call it that or not. We must rethink and refeel our nature and destiny. This may overstate the point, but religion is a highly important factor in the environmental crisis.
- T .C. McLuhan, (1971) Collection of Native American ideas about the earth, Touch the Earth: A Self-Portrait of Indian Existence (New York: Outerbridge and Dienstfrey,).
- Ari L Goldman, (1990) “Focus of Earth Day Should Be on Man, Cardinal Cautions,” New York.