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ENERGY BASICS

Energy Examples of energy.
When we consider the quantity force X distance, we are talking about work. Two things enter into every case where work is done. 1) the application of a force and 2) the movement of something by that force. Work = force x distance or W = Fd Work falls in two categories The unit of measurement for work combines a unit of force, N, with a unit of distance being M, the result of this is a joule.

Power Some examples of power
Power is the rate at which work is done. It equals the amount of work done by dividing the time interval during which the work is done. Power = work done over time interval The unit of power is joule per second, also known as the watt, in honor of James Watt.

Mechanical Energy Some examples of mechanical energy
Energy enables an object to do work Mechanical energy- the energy due to position of something, or the movement of something Mechanical energy can be in the form of either potential energy or kinetic energy, or the sum of the two.

Potential energy Some examples of potential energy
An object may store energy by virtue of its position The energy that is stored is called potential energy Chemical energy in fuels is also potential energy Work is required to elevate objects against the earth’s gravity The potential energy due to elevated positions is called gravitational energy Gravitational potential energy = weight x height PE = mgh

Kinetic energy Some examples of kinetic energy
If an object is in moving, then it is capable of doing work It has energy of motion, or kinetic energy The kinetic energy of an object depends on the mass of the object as well as its speed Kinetic energy = ½ mass x speed squared Net force x distance = kinetic energy Fd = ½ mv squared Whenever work is done, energy changes. This is the work-energy theorem

Conservation of energy
Some examples of conservation of energy The study of the various forms of energy and the transformation from one form into another led to one of the greatest generalizations in physics—the law of conservation of energy Energy cannot be created or destroyed It can be transformed from one form to another The welding of an atomic nuclei is called thermonuclear fusion and will be covered later.

Machines Some machines
A machine is a device used to multiply forces or simply to change the direction of forces When we do work on the end of a lever, the other end does not work on the load (force x distance) input = (force x distance) output The pivot point is also known as the fulcrum The ratio of the output force to the input force for a machine is the mechanical advantage A pulley is basically a kind of lever that can be used to change the direction of a force.

Efficiency Some examples of efficiency
An ideal machine would have 100% efficiency In any machine, some energy is transformed into atomic or molecular kinetic energy– making the machine warmer Efficiency can be expressed at the ratio of useful work output to total work input Efficiency = useful work output divided by total work input Efficiency = actual mechanical advantage divided by theoretical mechanical advantage

Energy for life Some examples of energy for life
Every living cell in every organism is a machine. Like any machine, living cells need an energy supply Only green plants and certain one-celled organisms can make carbon dioxide to combine with water to produce hydrocarbon compounds such as sugar. This process is known as photosynthesis and requires an energy input which normally comes from the sun

Review of chapter Some simple machines ETC.
When a constant forces moves and object in the direction of the force, the work done equals the product of the force and the distance the object is moved Power is the rate at which work is done The energy of an object enables it to do work Mechanical energy is due to the position of something (potential energy) or the movement of something (kinetic energy)

Review of Chapter, Continued
Some simple machines The law of conservation of energy states that energy cannot be created or destroyed Energy can be transformed from one form to another A machine is a device for multiplying force or changing the direction of force The lever, pulley, and inclined plane are simple machines The useful work output of a machine is less than the total work input

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