Principle Conservation Energy

LABUAN MATRICULATION COLLEGE SCIENCE INFORMATIC WS011 CONSERVATION OF ENERGY

GROUP MEMBER: 1. ADRIAN HO IK LIANG (MS0915542624) 2. MOHD. TARHAMIZI BIN ABD HAMID ( MS0915515816) 3. ZURINAH BINTI PAKEE ( MS0915517005) 4. DESMOND ANAK BONNIK (MS0915514779) 5. ELMA LIM ( MS0915514865)

LECTURER 'S NAME: MR. SYED NASIR BIN SYED AHMAD

Content

Title INTRODUCTION POTENTIAL ENERGY GRAVITATIONAL POTENTIAL ENERGY ELASTIC POTENTIAL ENERGY KINETIC ENERGY PRINCIPLE OF CONSERVATION ENERGY WORK-ENERGY THEROM CONCLUSION BIBLIOGRAPHY

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Introduction Conservation of Energy Energy is a very difficult concept to define. It is like trying to define money. We all know what to do with money, but we simply cannot define it without referring to what we do with it. The same is true of energy,although we have not generally developed money in our daily day or everdays lives. But we also think that energy as the currency of mother nature. Just as transfers and store of money are necessary for process to occur Financial World, transfer and store of energy are nessary for process to occur in our natural world. Besides that, energy is one of the most important concept in science field. But we cannot give a simple general definition of energy in only a fews fews words. In this conservation of energy, we can define translation of potential and kinetic energy. Later, we will know or examine others types of energy, such as that related to heat. The crucial aspect of all the types of energy is that the sum of all types and the total of energy is remain the same after any process occurs as it was before: that is the quantity “ energy “ can be difined so that it is a conserved quantity. Moreover, Conservation laws are the cornerstones of physics, both theoretically and practically. Most scientisc would probably name the conservation of energy as the most profound and far-reaching of these important laws to people. When we say something is conserved, it mean constant, or has a constant value. Because so many things continually change in physical processes, conserved quantities are extremely helpful in our attempts to understand and describe the universe. Keep in mine, though, that quantities are generally conserved only under special conditions. One of the important of the conservation laws is that concerning conservation of energy. A familiar statement is that the total energy of the universe is conserved. This is true because the whole universe is taken to be a system. A system is defined as a definite quantity of matter enclosed by boundaries, either real or imaginary. In effect, the universe is the largest possible closed, or isolated , system we can image. Within a closed system, particles can interact with each other but have absolutely no intreraction with anything outside.In generally then,the amounts of energy remain constant when on from the system.(including thermal enegy and radiation) 1

In another hand, energy is perhaps the concept most important to the science field or stream. The combination of the energy and matter made up the universe. Matter is substances and energy is the mover of the substances. Matter are things that we can see, smell, touch, taste or fel it. Matter is mass and occupied the space. Energy, on the other hand, it abstract. We cannot see, feel, taste, smell or touch of the most energy. Supprisingly, the idea of energy was unknown to Issac Newton, and its existence was still being debated in 1850s. Although energy is familiar to us now days,it still diffiuclt to define it because energy is not only “things” but both a thing and a process-as if it were both a noun and verbs. Persons, places, and things all have energy but we usually observe energy only when it undergoes change. Put another ways, energy is nature 's way to keeping score. We sence energy only when the score change or either when there is a transformation from one form of energy to another(as an example: when radian from the sun changes to thermal energy when it vibrates cells in our skin) or when there is a transfer of energy from another point to other point. Interestingly, just as water is composed of tiny lump( H2O molecules) energy changes also occurs in tiny lump or known as quanta. Within such a system energy may be converted, but the total among of all form of energy is constant or unchange.Totals of energy can never be create or destroy.

Potential energy Potential energy can be thought as energy stored within a physical system. Potential Enrgy is called because it has the potential to be change into other forms of energy, such as kinetic energy, and to do work in the process. The standard (SI) unit of measure for potential energy is the joule, the same as for work or energy in general. The term "potential energy" was coined by the 19th century Scottish engineer and physicist William Rankine.

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Gravitational Potential Energy As we know, there are two type of potential energy. One of the potential energy is gravitational potential energy. The gravitational potential energy is difened as the potential energy of a body due to the elevated position. For your information, the gravitational potential energy of an object is depands on its height from the grounds. Besides that, the object 's weight also influence the gravitational potential energy.

Therefore, if the height of an object form ground is higher, then the gravitational potential energy also become higher. As an example, when you lift an object upwards, its meants that you increase the gravitationalm potential energy of the object. Other than that, if the object is heaiver, then the gravitational potential energy will be greater when lifting it upwards. This is due to the energy transferred in lifting the object upwards. There are a few factors that affect the gravitational potential energy are its height relative to some referring point, its mass and the strength of the gravitational potential energy field in its.Thus, a book lying on a table has less gravitational potential energy than the same book on top of a taller cupboard, and less gravitational potential energy than a heavier book lying on the same table. It was important to notice that "height" is the common sense of the term that cannot be used for gravitational potential energy calculations when gravity is not assumed to be a constant.

In calculation, the formula that we must used to determine the gravitational potential energy is: change in gravitational potential energy = weight x change in height or change in gravitational potential energy = mgh 3

** example calculation that involved gravitational potential energy An althele of mass 50kg runs up a hill. The foots of the hills is 400m above the sea levels. The summit is 1200m above the sea level. By how much does the alhlete 's gravitational potential energy increase? [ acceleration due to the gravity g = ms-2] step 1: calculate the increase in height step 2: write down the equation for gravitational potential energy, then subtitute value and solve it. Change in gravitational energy = weight x change in height = mgh = 50kg x 10 ms¯² x 800m = 400000 so, the athelete gravitational potential energy increses by 400000 J.

Elastic Potential Energy Elastic Potentitial energy can be difined as the energy stored in in elastic materials as the result of their stretching or compressing.

Any spring that has been stretched or compressed had stored elastic potential energy. This mean that the spring is able to do work on another object by exerting a force over some distance as the spring resumes its original length. The energy stored in a spring is also called strain energy. The work done by a constant force,F is given by W=Fs, but this rule cannot be used to find work done by spring, because the forces that acts is not constant. The forces becomes larger as the extension increase. In this event, the area 4

under a force-displacement (F-s) graph is the work done on an object or the energy change that has occurred, we can use this approach to find the work done by a spring.

Fs
F

W = area under the Fs − x graph
W = 1 Fx1 2

W =

1 (kx1 ) x1 2

0

x

W =

x1

1 2 kx1 = U s 2

Kinetic Potential Energy The kinetic energy of a body can be defined as the amount of work it can do in coming to rest, or what amounts to the same thing,the amount of work that must have been done on it to increase it 's velocity from zero to it 's highest velocity.Kinetic energy also often called as the energy of motion.It is directly proportional to the square of the instantaneous speed of a moving object. A body of mass m, is moving with velocity, v: Kinetic Energy = 1/2 mv² kinetic energy is a positive, scalar quantity

To Show That Kinetic Energy = 1\2 mv² (variable force) Under the action of a force F, a body of mass m, suppose to be moves a small distances ðs.Though the force may be varying ðs is so small, the force can be considered constant over the distance ðs.The work done ðw is given equation as: ðw = Fðs If the force increases the velocity of the body from zero to v,the total work done W, is given by equation by:

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W = ∫Fds using Newton`s second law F = m dv/dt where dv\dt is the acceleration of the body.Then W = ∫m dv/dt ds remember that v = ds/dt W = ∫ mv dv and therefore, W = [½mv²]

The kinetic energy of a body depends only on it 's mass and it 's velocity. The kinetic energy is independent of the way in which the body needed this velocity. Hence, the result that has just been derived could have been obtained more simply by specifying that the body was accelerated by a constant force.

To Show That Kinetic Energy = ½mv² (constant force) If a body of mass m, moves a distance s, under the action of a constant force F, the work done W, by the force is given by the equation: W = Fs

If the acceleration is a, then from Newton`s second law F = ma, so

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W = mas if the body has been accelerated from rest to some velocity v, then v² = u² + 2as as = v²/2 then W = ½mv² therefore, kinetic energy = ½mv²

** example solve problem in kinetic energy. A stationary object of mass 3.0 kg is pulled upwards by a constant force of magnitude 50 N. Determine the speed of the object when it is travelled upwards through 4.0 m.

 F

 s

 F

 mg

 mg
(Given g = 9.81 m s-2) Solution: m=30.0kg ; F= 50 N; s = 4.0m and u=0 The nett forces acting on the object is given by: Fnett = F – mg = 50 – (30)(9.81) = 20.6 N By appling the work-kinetic energy therom, thus 7

Wnett = Kf + Ki Fnett s= ½ mv2 – 0 (20.6)(4.0) = ½ (3.0) v2 v = 7.41 ms-1

Principle of Conservation Of Energy Principle of conservation state that in any energy transformation, the total amount of energy before and after the transformation is constant. Energy cannot be created or destroyed. Energy only can be converted from one form to another or be transformed from one object to one object or place to place.
Σ Ei= Σ Ef

Ki + Ui = Kf + Uf

In generally, the amount of energy remains constant when no mechanical work is done on or by the system and no energy is transmitted to or from the system including thermal energy and radiation. Principle of conservation of mechanical energy states that total amount of mechanical energy( kinetic energy + potential energy) which the bodies posses in an isolated system is constant. It applies only to frictionless motion, for example, to conservative systems.

E=K+U total mechanical energy = potential energy + kinetic energy

The total mechanical energy is constant in a conservative system

Ei = Ef Ki + Ui = Kf + Uf ½ mivi2 + mighi = ½ mfvf2 + mfghf 8

In system with non-conservative force, the total mechanical energy is changed. The work done by the non-conservative forces acting on an object is equal to the total change in kinetic and potential energy.

WNL = Since the change in kinetic energy can be the result of many types of forces, it is conservent to separate

 KE into three part:

1. The change in kinetic energy due to the internal conservatite forces, 2. The change in kinetic energy due to internal conservatite force,

 Kinf −c

 Kinf −nc

3. The change in kinetic energy due to external forces ( conservative or nonconservatite servative),

 Kexf

 K = Kint−c Kint −nc Kext or  Kfui Kint−nc K ext= KU  f

Conservatite forces are forces for which the work done does not depand on the path taken but only on the initial and final positions. Non-conservatite forces are forces for which the work done depands on the path taken.

Example of conservatite forces: I. Gravitational forces II. The spring forces III. Electric

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Example of non-conservatite forces: I. Friction II. Air resistance III. Tension in cord IV. Motor or rocket propulsion V. Bush or pull by a person

From a universal point of view, the total energy of the universe is constant. If the part of the universe gains energy in some forms, another part must lose an equal amount of energy. No violtion of this principle has been found. The total energy is always conserved as long as all forms of energy are accounred. **Example of energy that energy transferred to kinetic energy.

Demonstration When a pendulum is displaced, it gains gravitational potential energy due to its increased height. When subsequently released, this energy becomes transferred to kinetic energy. This data logging experiment explores the relationship between these changes of energy. Apparatus and materials: Light gate, interface and computer Pendulum Stand, clamp and boss

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Ruler in clamp Micrometer Electronic balance

Technical notes 1.Set up the apparatus so that the stationary pendulum bob hangs exactly in front of the light sensor, interrupting the light beam.

2.Connect the light gate via an interface to a computer running data-logging software. The program should be configured to obtain measurements of kinetic energy. These are derived from the interruption of the light beam by the pendulum bob - this moves a distance equal to its diameter during the interruption time.

3.The internal calculation within the program requires the mass and diameter of the bob to be entered into the software, so that the velocity of the bob and kinetic energy are calculated. Measure the diameter using a micrometer. Measure the mass using an electronic balance with a sensitivity of 0.01 g. Accumulate the series of results in a table. This should also include a column for the manual entry of displacement height measurements, taken from the ruler.

Safety Read our standard health & safety guidance

Procedure Data collection a . Displace the bob so that it is raised 1.0 cm above its rest height as shown above. Hold the bob against the ruler. Note the reading for the point of contact which is on a level with the centre of the bob. Release carefully and allow it to perform ONE swing to and fro. This should produce two lines of data in the table, corresponding to the forward and back parts of the swing. Repeat this five times. The table shows ten values. 11

b. Enter 1.0 cm in the 'height fallen ' column. c. Repeat this procedure for heights of 2, 3, 4 and 5 cm.

Analysis

Depending upon the software, the results may be displayed on a bar chart as the experiment proceeds. Note the increase in values of kinetic energy as the height fallen is increased. Investigate the relationship between kinetic energy and height fallen more precisely by plotting a XY graph of these two quantities. (Y axis: kinetic energy; X axis: height fallen) This usually gives a straight line indicating proportionality. Use a curve- matching tool to identify the algebraic form of the relationship.

The gravitational potential energy lost depends in direct proportion upon height fallen. Therefore the straight line graph indicates that kinetic energy gained is proportional to potential energy lost.

Teaching notes:

1.Students can add a further column to the table, to calculate the potential energy lost from the height fallen, using m g Δh. Care is needed with units. In view of the small values of energy, it may be useful to calculate energy values in millijoules. Calculation of potential energy should yield values numerically the same as the corresponding kinetic energy. This would support the Law of Conservation of Energy. 2. If the results are less than convincing, discuss the potential sources of error. Prime suspects must be the measurements performed using the ruler, micrometer and scales. 12

* Notes: this experiment was submitted by Laurence Rogers, Senior Lecturer in Eduction at Leicester University. This experiment was checked in May 2006.

Work Energy Theorem

Work energy theorem is difined as that work done by an object is the same as the change of the object 's kinetic energy. The equation derived:

Wtotal =

K

= ½ mvf2 - ½ mvi2 Altough this equation for a force that is constant in direction and magnitude, it also valid for any forces, thus making the work-energy therom is generally. The work in the work energy theorem equation also defined as the net work or work based on the net force. For instance if we push a box. W = Fs is equal to Fnets = ½mvf² – ½mvi² However, only partial of the total work responsible for the change of the objects kinetic energy while the rest is lost in form of heat energy.

Work-energy theorem is created by the relationship between concept of work with resultant force and the change in kinetic energy. By moving a body of mass m, along the xaxis with the constant resultant force F, directed along the axis, the body`s acceleration is constant and given by Newton`s Second Law of motion with the body`s gain velocity over time thus changing the body`s kinetic energy and will undergoes displacement,s.

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Replace the v and u with vf and vi respectively v² = u² + 2as vf² = vi² + 2as where a = vf² – vi² 2s we multiply both side with m

ma = m(vf² – vi²) 2s where F = ma F = mvf² – mvi² 2s and Fs = ½mvf² – ½mvi² where Fs = work done = W ½mv² = kinetic energy = kE W = kEf – kEi W = ∆kE

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Conclusion

In conclusion, energy is needed to some work. Besides that, energy also are important to the science field. As we know that energy divide two part that is potential energy and kinetic energy. Potential energy can be difined as the energy stored in a body or system because of its position, shape or state. Potential energy also divided into two part of energy which is gravitational energy and elastic potential energy. Gravitational potential energy can be difined as the energy stored in a body or system because of its position. Besides that, elastic potential energy also difined as the energy stored in elastic materials as the result of their streching or compressing. Example of materials that applies elastic potential energy is spring and rubber band. Kinetic energy can be defined as the energy of a body due its motion. Example of kinetic energy is roller coaster.

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Bibliography

1. Jerry D. Wilson and Anthony J. Buffa(2001),College Physics(forth edition), Prenficehall inc. 2. Tom Duncan(2000) Advanced Phyiscs ( Forth edition), John Murray Ltd. 3. David Sang (2001), Phyiscs, University Of Cambridge. 4. Douglas C. Giancoli ( 2005), Phyiscs Principle With Application ( sixth edition), Pearson Eduacation Internatioanl. 5. James S. Walker(2004) Phyiscs Sec. Edition, Pearson Eduaction Inc. 6. Francis W. Sears(1991) College phyiscs ( seventh edition), Addison-Wesly. 7. Geoff Millar, Rob chapman, Henry Gersh, Keith Burrows, Doug Bail and Carmel Fry (1996) Phyiscs 12 units 3 and 4, Heinenam 8. Hewitt Suchocki Hewitt (1999) Conceptual Physical Science ( second edition) , Addision Wesley 9. Thomas A. Moore (2003), Six Idea That shaped Phyics, UnitN: The laws Of Physics are Universal ( Second Edition), Mcgraw -Hill Higher Education. 10. Micheal browne (2004) Physics For Engineering And Science, Mc Graw Hill Companies Inc.

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Bibliography: 1. Jerry D. Wilson and Anthony J. Buffa(2001),College Physics(forth edition), Prenficehall inc. 2. Tom Duncan(2000) Advanced Phyiscs ( Forth edition), John Murray Ltd. 3. David Sang (2001), Phyiscs, University Of Cambridge. 4. Douglas C. Giancoli ( 2005), Phyiscs Principle With Application ( sixth edition), Pearson Eduacation Internatioanl. 5. James S. Walker(2004) Phyiscs Sec. Edition, Pearson Eduaction Inc. 6. Francis W. Sears(1991) College phyiscs ( seventh edition), Addison-Wesly. 7. Geoff Millar, Rob chapman, Henry Gersh, Keith Burrows, Doug Bail and Carmel Fry (1996) Phyiscs 12 units 3 and 4, Heinenam 8. Hewitt Suchocki Hewitt (1999) Conceptual Physical Science ( second edition) , Addision Wesley 9. Thomas A. Moore (2003), Six Idea That shaped Phyics, UnitN: The laws Of Physics are Universal ( Second Edition), Mcgraw -Hill Higher Education. 10. Micheal browne (2004) Physics For Engineering And Science, Mc Graw Hill Companies Inc. 16