Work, Energy, & A ; Power Essay, Research Paper

Work

Work is said to be done when the point of application of a force moves and is measured by the merchandise of the force and the distance moved in the way of the force.

Work = force ten distance moved in way of the force

The SI unit of work is called the J ( J ) and is the work done when the point of application of a force of 1 Newton ( N ) moves through 1 metre ( m ) in the way of the force. Larger units used are the kilojoules ( kJ ) and the mega J ( MJ ) .

1 kJ = 1,000 J ( or 103 J )

1 MJ = 1,000,000 J ( or 106 J )

It follows that an engine which exerts a force of 9000 N over a distance of 6 m will make 9000 x 6 = 54 000 J, or 54 kJ.

Energy

Anything which is able to make work, as defined above, is said to possess energy, and hence

Energy is the capacity to execute work.

It may take many signifiers, such as atomic, chemical, heat, mechanical or electrical energy. If we ignore the theoretical atomic natural philosophies, which ne’er affects electrical-craft work, it is true to state that, whereas energy can be converted from one from one signifier to another, it can be neither created nor destroyed. For case, coal, or oil, incorporating chemical energy, is burned in the boilers of a power station, and produces heat. This heat evaporates H2O to go steam under force per unit area, which is fed to a turbine where mechanical energy is produced heat. This turbine drives an alternator, which produces electrical energy. The unit of energy is the same as the work it is capable of executing, i.e. the metre Newton ( J ) or in other words

Mechanical Energy

In mechanics, energy is divided into two sorts called possible and kinetic energy severally ( brief p.e. and k.e. ) .

Kinetic energy is the energy, which a organic structure has by ground of its gesture.

Potential energy is the energy something has by ground of its place or province.

k.e. = ? mv2 and p.e. = Mgh

Where:

M = mass ( in kgs )

g = gravitation ( 9.81 )

H = tallness ( in metres )

V = speed ( in m/s )

Obvious illustrations of kinetic energy are traveling slugs or hammer caputs. These are able to make work by get the better ofing forces when they strike something. A heavy flywheel shops energy in the signifier of rotational kinetic energy and so maintain an engine running swimmingly in between the working shots of its Piston.

One of the commonest signifiers of possible energy is that possessed by a organic structure when it is above the degree of the Earth & # 8217 ; s surface. When something is lifted vertically, work is done against its weight and this work becomes stored up in the organic structure as gravitative possible energy.

Another illustration is the elastic possible energy stored up in a wound clock-spring.

Electrical Energy

Basically, an electric current is a motion or flow of minute atoms called negatrons. Each negatron has the same charge of electricity and the motion of these atoms leads to the development of kinetic of possible energy.

Chemical Energy

Energy that is stored in affair and released during a chemical reaction, such as T

he burning of a fuel.

Thermal Energy

A signifier of energy straight associated with and relative to the random motion of molecules of a substance. This motion may be diversely generated by burning, clash, chemical action, radiation, etc.

Transformation of energy from one sort to another

The jurisprudence of preservation of energy which was mentioned earlier provinces that energy is neither created nor destroyed but merely alterations from one signifier to another. Work and energy are, both measured in the same units, viz. , Js. The universe we live in provides energy in many different signifiers, of which the most of import has been, chemical energy. The use of the latent chemical energy in coal, oil and gas, released in the signifier of heat to drive watercourse turbines and internal-combustion engines, has been a major factor in the development of modern civilisation.

Power and its units

Machines may be classified by the velocity with which they do work ; therefore there are motorcar engines of little & # 8220 ; power & # 8221 ; , as they are rated, or big power.

Power is defined as the rate of making work,

or mean power = work done

Time taken

The SI units of power is called the W ( W ) and is a rate of working of 1 J per second

Therefore, 1 W = 1 J/s

Larger units used are the kW ( kilowatt ) and the megawatt ( MW )

1 kilowatt = 1 000 W ( or 103 W )

1 MW = 1 000 000 W ( or 106 W )

Worksheet

1 ) Calculate the power of a pump which can raise 200 kilogram of H2O through a perpendicular tallness of 6 m in 10 s. ( Assuming g = 9.81 m/s2 )

2 ) A male child whose mass is 40 kilogram discoveries that he can run up a flight of 45 stairss, each 16 centimeter high, in 5.2 s. ( Assuming g = 9.81 m/s2 )

3 ) A adult male whose mass is 75 kilogram walks up a flight of 12 stairss each 20 centimeter high in 5 s. Find the power he develops in Watts?

4 ) A perpendicular force of 58 720 N lifts a vehicle through a distance of 1.5 m on a hydraulic incline of hoist. Find the power required to raise it in ( a ) ? min, ( B ) ? min, ( degree Celsius ) 1 min.

5 ) A package of conduit has a mass of 200 kilogram. What is its weight? What work must be done in raising the conduit from the floor on to a table rack 2 m high?

6 ) A force of 100 N will merely travel a new wave on a degree route. What work will be expended in forcing the new wave 15 m?

7 ) An electric motor drives a pump which lifts 1000 L ( litres ) of H2O each minute to a armored combat vehicle 20 m above normal H2O degree. What power must the motor provide if the pump is 50 % efficient? 1L of H2O weighs 9.81 N.

8 ) A sling is marked as holding a safe working burden of 2000 kilogram. What weight will it back up safetly?

9 ) A machine requires a force of 500 N to raise it. What is its mass?

10 ) The gasoline engine of a builder & # 8217 ; s hoist is to be replaced with an electric motor. What should be he evaluation of the motor if it must be capable of raising 2400 N through 32 m in 24 seconds, the hoist cogwheel being 80 % efficient?

Note that efficiency is:

Efficiency = input x 100 %

End product

Bibliography

Motor Vehicle Mechanics: Third Edition

By Technitians Examinations of the City and Guilds of LOndon Institute.