Mis Konsepsi Mencair Es di Kutup akan Menenggelamkan Pulau

Oleh

Desmalinda,M.Pd

Guru SMAN 10 Padang

Isu tentang peninggkatan suhu bumi selalu di lancarkan dan di barengi dengan pencairan es di kutup dan dikomentari pencairan es akan menyebabkan beberapa pulau akan tenggelam.Pernyataan inilah salah satu mis konsepsi tentang es yang terapung di permukaan air, tp slalu di dengungkan,. kenapa saya bilang miskonsepsi? karena ndak sesaui dengan kenyataan dan hukum fisika tentang fluida gaya apung oleh Archimedes.

Menurut hukum archimedes Gaya apung/ gaya keatas adalah juka benda dicelupkan/tercelup kedalam zat cair sabagian atau seluruhnya maka benda tersebut mendapat gaya keatas sebesar berat benda yang dipindahkan. artinya jika ada benda yang terapung di atas zat cair maka volume benda yang tercelup ke dalam zat cair itu sama dengan volume yang dipindahkan oleh benda ke zat cair, artinya lagi jika ada es yang terapung di atas air, maka jika es mencair volume es mencair tidak akan menambah volume air karena volume es yang mencair menempati volume es tadi.

Hal ini dapat di buktikan dengan percobaan sederhana, ambillah segealas air masukkan es kedalam air sampai es dapat terapung diatas air, sehingga dapat membentuk gunung es dalam gelas.yang berisi air. Pastikan air pas penuh sampai bibir gelas dan es ada yang terapung di atas gelas. biarkan semua es mencair, maka amatilah apa yang terjadi? jika semua es sudah mencair tidak ada Volume air yang tumpah dari gelas akibat mencairnya es tersebut.

Maka andaikan memang terjadi peninggkatan suhu di bumi dan kutup Es mencair maka volume air di bumi tidak akan bertambah, karena volume air itu menempati volume es yang sudah mencair, permukaan air laut tidak akan naik walaupun es di kutup mencair, jadi tidak ada pulau yang akan tenggelam akibat kutup es mencair. Jadi yang didengungkan selama ini oleh global warning ini kurang tepat.

Demikian shering singkat saya, mudah-mudahan ada manfaatnya bagi kita semua. amin.

Wassalam

Desmalinda,M.Pd.

RPP Work and Energy

PEMERINTAH KOTA PADANG

DINAS PENDIDIKAN

SEKOLAH MENENGAH ATAS(SMA) NEGERI 10 PADANG.

Situjuh Telp (0751)27331 Padang Kode Pos 25129

LESSON PLAN

WORK AND ENERGY

A. Identities

Subject	: Physics
Class/semester	: XI / I
Meeting to	: 3, 4
Time Allocation	: 2 x 45 minutes
Standard competency	: Analyze physics phenomena and it’s regularly in scope mechanics particle object
Base competency	: Analyze relationship between work, energy change and the Law of Conservation of Mechanical Energy
Indicators	: Describe relationship among work, force, displacement

A. Learning objectives : - The students are able to :

1. Observe requirement of work

2. Calculate the work done by force on smooth plane through experiment

3. Calculate the work done by force on incline plane through experiment

4. Calculate the work by several forces

5. Calculate the work from F-x graph

B. Learning materials : 1. Work is product of force with displacement which is in the same direction

The work W done on an object by an agent exerting a constant force on the object is the product of the component of the force in the direction of the displacement and the magnitude of the displacement:

2. Factors influence the magnitute of work

3. Formulation of work is:

W = F cos θ.∆x

4. Work by several forces :

W = W₁ + W₂ + W₃ +……….

KINETIC ENERGY AND THE WORK – KINETIC ENERGY THEOREM

Figure shows a particle of mass m moving to the right under the action of a constant net force ∑F. Because the force is constant, we know from Newton’s second law that the particle moves with a constant acceleration a. If the particle is displaced a distance d, the net work done by the total force ∑F is

We found that the following relationships are valid when a particle undergoes constant acceleration:

where vi is the speed at t _ 0 and vf is the speed at time t. Substituting these expressions into Equation gives

The quantity represents the energy associated with the motion of the This quantity is so important that it has been given a special name kinetic energy. The net work done on a particle by a constant net force F acting on it equals the change in kinetic energy of the particle. In general, the kinetic energy K of a particle of mass m moving with a speed v is defined as

Kinetic energy is a scalar quantity and has the same units as work.

in the form

C. Learning methods: experiment, discussion, task

D. Stages of learning activities

No	Learning activities	Time allocation	Sources/Material /Tools
1	Opening activities Ø Teacher checks students attendance Ø students collect the previous task of report Ø Apperception: § Is it the same the definition of work in physics with the term of work known in daily life? Ø Motivation : § Is lifter that lift the told do the work? If that lifter hold back the load on it, does it belong doing the work? Ø Teacher delivers base competency about : § Analyze relationship between work, energy change and the Law of Conservation of Mechanical Energy analysis. Main Activity Exploration · The students sit in group · Teacher give LKS Elabiration · Student do experiment that is suitable with guidance in LKS and discuss the result in group. The teacher goes around to control and be ready to help the students if needed · From the data got the students do analyzing so that can write the conclusion by making pratical report · The students mention application samples of work concept of daily life Confirmation · Teacher give some concept applications in determine resultant of work an energy of object in daily life. · Teacher gives examples of physics problem to determine the work and energy . The students look and write example of physics problem and it’s solution that given by teacher. Closing Activities · Teacher checks concept mastery of students and make the conclusion together. · Teacher gives award to group that has good work and relationship. · Teacher gives homework to student and task student to read material that will be studied in the next meeting	10’ 10’ 5’ 5’ 40’ 5’ 5’ 5’ 5’ 5’ 5’ 5’	Sources : a. physics book of class XI semester 1 b. Relevance of reference book c. Work sheet (LKS) d. Tools and material of experiment

E. Assesment.

a. Observation format

b. Performance

1. Consider a tug-of-war in which two teams pulling on a rope are evenly matched so that no motion takes place. Assume that the rope does not stretch. Is work done on the rope? On the pullers? On the ground? Is work done on anything?

2. For what values of _ is the scalar product (a) positive and b) negative?

3. As the load on a spring hung vertically is increased, one would not expect the Fs-versus-x curve to always remain linear, as shown in Figure 7.10d. Explain qualitatively, what you would expect for this curve as m is increased.

4. Can the kinetic energy of an object be negative? Explain.

5. (a) If the speed of a particle is doubled, what happens its kinetic energy? (b) If the net work done on a particle is zero, what can be said about the speed?

6. A tugboat exerts a constant force of 5 000 N on a ship moving at constant speed through a harbor. How much work does the tugboat do on the ship in a distance of 3.00 km?

7. A shopper in a supermarket pushes a cart with a force of 35.0 N directed at an angle of 25.0° downward from the horizontal. Find the work done by the shopper as she moves down an aisle 50.0 m in length.

8. A raindrop (m _ 3.35 10_5 kg) falls vertically at constant speed under the influence of gravity and air resistance. After the drop has fallen 100 m, what is the work done (a) by gravity and (b) by air resistance?

9. A sledge loaded with bricks has a total mass of 18.0 kg and is pulled at constant speed by a rope. The rope is inclined at 20.0° above the horizontal, and the sledge moves a distance of 20.0 m on a horizontal surface. The coefficient of kinetic friction between the sledge and the surface is 0.500. (a) What is the tension of the rope? (b) How much work is done on the sledge by the rope? (c) What is the energy lost due to friction?

10. A block of mass 2.50 kg is pushed 2.20 m along a frictionless horizontal table by a constant 16.0-N force directe 25.0° below the horizontal. Determine the work done by (a) the applied force, (b) the normal force exerted by the table, and (c) the force of gravity. (d) Determine the total work done on the block.

11. A 15.0-kg block is dragged over a rough, horizontal surface by a 70.0-N force acting at 20.0° above the horizontal. The block is displaced 5.00 m, and the coefficient of kinetic friction is 0.30

12. Find the work done by (a) the 70-N force, (b) the normal force, and (c) the force of gravity. (d) What is the energy loss due to friction? (e) Find the total change in the block’s kinetic energy

13. A person lifts an object of mass 1,5 kg vertically upward through a distance of 2.0 m with constant speed. Determine (a) the work done by the person, (b) the work done by the gravitational force,(c) the total work by the two force.

14. An object of mass 1.5 kg slides downwards on a smooth Inclined plane AC of length 25.0 m. Determine the work Done by the gravitational force in order to displace the Object from A to B.

KNOW BY PADANG, 25 JUNI 2010

PRINCIPLE R VICE PRINCIPLE PHYSICS TEACHER

DRS.Safarni Budaya Putra Haryanti,M.Pd Desmalinda, S.Pd,

NIP : 19501122 197903 1005 NIP : 196807171995122002 NIP : 19671205 199702 2 001

bandul2

LESSON PLANE.

SCHOOL : SMA N 10 PADANG

CLASS : XI INTERNATIONAL

SUBJECT : PHYSICS

TOPICS : THERMODYNAMIC

STANDARD COMPETENCE : To Apply the concept of Thermodynamics in heat mechine

BASIC COMPETENCE : To analyze the changing varables of ideal gas by applicating the law of thermodynamics..

INDICATORS for studying:

a. By repeating the result of model theory Kinetic’s experiment the student be able to

1. Recall the relationship between Energy kinetics and temperature in equipartisie Energy of particle. ,
2. Formulate the Inners energy in gas.
3. recall the relationship between Pressure ( P ) and Volume ( V ),Temperature and n ( mole gas )

b. by using presentation power point which gas give a heat student be able to

1. . analyze the work which is gas doing in variable conditions of gas .

2. Formulate the first law of Thermodynamics.
3. analyze the first law of thermodunamic in variable conditions of gas

c. by using diagram Carnot machine the student can be able to describe the relationship between heat absorptions ,work and heat releasing .and describe the maximum efficiency of Carnot machine

d. by using diagram of Refrigerator machine the student can be able to describe the relationship between heat absorptions ,work and heat releasing .and describe the maximum efficiency of machine ..

ESSENTIAL MATTERS:

Gas always move with Brown Motion except O^o K.it is called Absolute zero temperature and each direction has kinetic Energy = ½ kT ( k=bolztman constant , T=temperature in Kelvin.) statement of Maxwel.

	So the Kinetic’s Energy of ideal gas = 3/2 n R T

If one direction of motions the kinetic’s energy is ½ kt the kinetic’s energy total for :

1. Helium gas in lower temperature = 3/2 kT

medium temperature = 3/2 kT

higher temperature = 3/2 kT.

So Mono atomic gas just only move with three direction of translations

2. Oksigen gas in lower temperature = 3/2 kt

medium temperature = 3/2 kT + 2/2 kT = 5/2 kT

higher temperature = 3/2 kt + 2/2 kT + 2/2 kT = 7/2 kT

3. Ozon Gas . in lower temperature = 3/2 kT

medium temperature =3/2 kT + 3 x 2/2 kT = 9/2 kT

higher temperature =3/2 kT + 3x 2/2 kT +3x 2/2 kT = 15/2 kT

So Ideal Gas is all gasses in lower temperature it has kinetic’s energy = 3/2 kT for one molekul but in tube there are N molecules Ek = 3/2 N k T = 3/2 n R T.

We have found the equation if ideal gas like the equations below :

	P.V = n R T ( Boyle Gay Lussac )

EXTERNAL WORK :

External Work = W = P.∆V = P ( V₂ – V₁ ) for pressure constant

If the pressure is changing the work can find by calculating the area of P-V diagram.

There are four process in thermodynamic :

Isobaric Process:

P W = P ( V₂ – V₁ )

0 V₁ V₂

Isochoric Process : Vokume is constant so W = zero = 0

Isotermic Process : Pascal

It can be calculate ~ area of trapezium

P₁ = 4 dW = P dV

dW = nRT/V dV

∫dW = nRT ∫V^-1 dV

P2 = 1 W = nRT ( ln V₂ – ln V₁ )

W = P₁V₁ ( ln V₂ – ln V₁ )

0 1 2 3 4

Adiabatic Process : P₁.V₁^γ = P_2.V₂^γ γ = laplace’s constant = 1,3

For finding this work just to make grap and calculate the area of P-V.

Thermodynamic’s Law :

ACTIVITY:

Preface : The teacher thanks to God , and then ask the chairman to pray to God 5’

Using Computer for showing the Topics and Indicators. 5’

Action : Informasi About Kinetics Theory Model and principle of Equiparticy 15’

Energy of gas .

Till find the equation of velocity.

Ask Danu to take place in front of the class for lead the practicer 5’

And group A will do the experiment no 1,2,3, and one of the member in 15’ group writte the result on the stricker and put it on the board and talking about the conclusion .

So follow with group B and C and Danu still the leader for practice 30’

One of them make all conclusion for formulate the relationship among 15’ P.V.T and n,R

Checlist:Ask the student for describe what has they found in this activity. 10’

Exercise with 2 problem 20’

120’

Problem :

1. Soal fisika UMPTN 99 Rayon B No. 27

B A

3N` N

300 K

volume B = 2 x volume tabung A, both containing gas ideal.The volume of tube that connect A to B is smallaest equal zero. Gass A has temperature 300 K.total molecul in A = N and in B = 3 N, so the temperature B is;

(A). 150 K (B). 200 K (C). 300 K (D). 450 K (E). 600 K

2. A container hold gas at 27^oC To what temperature must it be heated for the pressure to double ? Assume the volume of the gas remains unchanged .

Signature ,Head Master Padang,22 February 2008

Physics teacher.

Drs.H.Safarni Budaya Putra Desmalinda

Nip : 130 784 576 Nip : 132 169 759

LESSON PLANE.

SCHOOL : SMA N 10 PADANG

CLASS : XI INTERNATIONAL

SUBJECT : PHYSICS

TOPICS : THERMODYNAMIC

STANDARD COMPETENCE : To Apply the concept of Thermodynamics in heat mechine

BASIC COMPETENCE : To analyze the changing varables of ideal gas by applicating the law of thermodynamics..

INDICATORS for studying:

a. By repeating the result of model theory Kinetic’s experiment the student be able to

1. Recall the relationship between Energy kinetics and temperature in equipartisie Energy of particle. ,
2. Formulate the Inners energy in gas.
3. recall the relationship between Pressure ( P ) and Volume ( V ),Temperature and n ( mole gas )

b. by using presentation power point which gas give a heat student be able to

1. . analyze the work which is gas doing in variable conditions of gas .

2. Formulate the first law of Thermodynamics.
3. analyze the first law of thermodunamic in variable conditions of gas

c. by using diagram Carnot machine the student can be able to describe the relationship between heat absorptions ,work and heat releasing .and describe the maximum efficiency of Carnot machine

d. by using diagram of Refrigerator machine the student can be able to describe the relationship between heat absorptions ,work and heat releasing .and describe the maximum efficiency of machine ..

ESSENTIAL MATTERS:

Gas always move with Brown Motion except O^o K.it is called Absolute zero temperature and each direction has kinetic Energy = ½ kT ( k=bolztman constant , T=temperature in Kelvin.) statement of Maxwel.

	So the Kinetic’s Energy of ideal gas = 3/2 n R T

If one direction of motions the kinetic’s energy is ½ kt the kinetic’s energy total for :

1. Helium gas in lower temperature = 3/2 kT

medium temperature = 3/2 kT

higher temperature = 3/2 kT.

So Mono atomic gas just only move with three direction of translations

2. Oksigen gas in lower temperature = 3/2 kt

medium temperature = 3/2 kT + 2/2 kT = 5/2 kT

higher temperature = 3/2 kt + 2/2 kT + 2/2 kT = 7/2 kT

3. Ozon Gas . in lower temperature = 3/2 kT

medium temperature =3/2 kT + 3 x 2/2 kT = 9/2 kT

higher temperature =3/2 kT + 3x 2/2 kT +3x 2/2 kT = 15/2 kT

So Ideal Gas is all gasses in lower temperature it has kinetic’s energy = 3/2 kT for one molekul but in tube there are N molecules Ek = 3/2 N k T = 3/2 n R T.

We have found the equation if ideal gas like the equations below :

	P.V = n R T ( Boyle Gay Lussac )

EXTERNAL WORK :

External Work = W = P.∆V = P ( V₂ – V₁ ) for pressure constant

If the pressure is changing the work can find by calculating the area of P-V diagram.

There are four process in thermodynamic :

Isobaric Process:

P W = P ( V₂ – V₁ )

0 V₁ V₂

Isochoric Process : Vokume is constant so W = zero = 0

Isotermic Process : Pascal

It can be calculate ~ area of trapezium

P₁ = 4 dW = P dV

dW = nRT/V dV

∫dW = nRT ∫V^-1 dV

P2 = 1 W = nRT ( ln V₂ – ln V₁ )

W = P₁V₁ ( ln V₂ – ln V₁ )

0 1 2 3 4

Adiabatic Process : P₁.V₁^γ = P_2.V₂^γ γ = laplace’s constant = 1,3

For finding this work just to make grap and calculate the area of P-V.

Thermodynamic’s Law :

ACTIVITY:

Preface : The teacher thanks to God , and then ask the chairman to pray to God 5’

Using Computer for showing the Topics and Indicators. 5’

Action : Informasi About Kinetics Theory Model and principle of Equiparticy 15’

Energy of gas .

Till find the equation of velocity.

Ask Danu to take place in front of the class for lead the practicer 5’

And group A will do the experiment no 1,2,3, and one of the member in 15’ group writte the result on the stricker and put it on the board and talking about the conclusion .

So follow with group B and C and Danu still the leader for practice 30’

One of them make all conclusion for formulate the relationship among 15’ P.V.T and n,R

Checlist:Ask the student for describe what has they found in this activity. 10’

Exercise with 2 problem 20’

120’

Problem :

1. Soal fisika UMPTN 99 Rayon B No. 27

B A

3N` N

300 K

volume B = 2 x volume tabung A, both containing gas ideal.The volume of tube that connect A to B is smallaest equal zero. Gass A has temperature 300 K.total molecul in A = N and in B = 3 N, so the temperature B is;

(A). 150 K (B). 200 K (C). 300 K (D). 450 K (E). 600 K

2. A container hold gas at 27^oC To what temperature must it be heated for the pressure to double ? Assume the volume of the gas remains unchanged .

Signature ,Head Master Padang,22 February 2008

Physics teacher.

Drs.H.Safarni Budaya Putra Desmalinda

Nip : 130 784 576 Nip : 132 169 759