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ENERGY. Energy describes a system’s ability to cause change. A system that has energy has the ability to do work. Mechanical energy is the energy possessed by an object due to its motion or its position. Potential energy and kinetic energy are both forms of mechanical energy.
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Energy describes a system’s ability to cause change. A system that has energy has the ability to do work.
Mechanical energy is the energy possessed by an object due to its motion or its position. Potential energy and kinetic energy are both forms of mechanical energy.
Chemical energy is a form of energy stored in molecules. Batteries are storage devices for chemical energy.
Electrical energy comes from electric charge, which is one of the fundamental properties of all matter.
Nuclear energy is a form of energy stored in the nuclei of atoms. In the Sun, nuclear energyis transformed to heat that eventually escapes the sun as radiant energy.
Radiant energy is energy that is carried by electromagnetic waves. Light is one form of radiant energy.
The electromagnetic spectrum includes visible light, infrared radiation (heat), and ultraviolet light. Light energy and heat energyare included in the electromagnetic spectrum.
The workings of the universe can be viewed as energy flowing from one place to another and changing back and forth from one form to another.
Potential Energy • Objects that have potential energy do not use the energy until they move. • An object’s potential energy comes from the gravity of Earth. • Technically, energy from height is called gravitational potential energy. • Other forms of potential energy also exist, such as potential energy stored in springs.
Potential Energy Mass (kg) Ep = mgh Potential Energy (joules) Height (m) Acceleration of gravity (m/sec2)
Systems or objects with potential energy are able to exert forces (exchange energy) as they change. Potential energy is energy due to position.
Energy of motion is called kinetic energy. The kinetic energy of a moving object depends on two things: mass and speed. Kinetic energy is proportional to mass. Kinetic Energy
Mathematically, kinetic energy increases as the square of speed. If the speed of an object doubles, its kinetic energy increases four times (mass is constant).
Kinetic Energy KE (joules) mass of object (kg) EK = ½ mv2 velocity (m/sec)
Energy of motionis called kinetic energy. A moving cart has kinetic energy because it can hit another object (like clay) and cause change.
Kinetic energy becomes important in calculating braking distance.
Pushing a 1-kilogram object with a force of one newton for a distance of one meter uses one joule of energy. A joule (J) is the S.I. unit of measurement for energy.
One joule is a pretty small amount of energy. An ordinary 100 watt electric light bulb uses 100 joules of energy every second!
Sources of energy The chemical potential energy stored in the food you eat is converted into simple sugars that are burned as your muscles work against gravity as you move.
Systems change as energy flows and changes from one part of the system to another. Each change transfers energy or transforms energy from one form to another.
As energy takes different forms and changes things by doing work, nature keeps perfect track of the total. No new energy is created and no existing energy is destroyed.
Conservation of Energy The idea that energy transforms from one form into another without a change in the total amount is called the law of conservation of energy. The law of energy conservation says the total energy before the change equals the total energy after it.
The conservation of energy is most useful when it is applied to a closed system. Because of the conservation of energy, the total amount of matter and energy in your system stays the same forever.
How can we predict how energy will change? One thing we can always be sure of is that systems tend to move from higher to lower energy.
The total energy in the system is the potential energy of the ball at the start. • Later, the ball is at a lower height (h) moving with speed (v) and has both potential and kinetic energy.
When you throw a ball in the air, the energy transforms from kinetic to potential and then back to kinetic.
The word workhas a very specific meaning. • Workis the transfer of energy that results from applying a force over a distance. Work (joules) = Force (newtons) distance (meters) W = F d
Regular (incandescent) light bulbs convert only 10% of electrical energy to light. That means 90% of the energy is released as wasted heat.
