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UNIVERSITY OF GUYANAFACULTY OF NATURAL SCIENCESDEPART. OF MATH, PHYS & STATS

PHY 110 – PHYSICS FOR ENGINEERSLECTURE 4

(THURSDAY, SEPT. 15, 2011)

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Lecture Notes:

For this information, visit my website:

http://ugphysics.weebly.com

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Assessments:

Group Assignment # 1 due on Friday September 23, 2011.Power Point Presentations

1. 1.8_Radiation.2. 1.9_First Law of Thermodynamics. Heat

& Work.

NB: The written report is due before the oral presentation is done. Its main content is at least five (5) pages in length, double spacing.

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Assessments Cont’d:

Tutorial Groups are Assignment Groups:

1. Mondays – 12:15 p.m. (Mechanical Eng.)

2. Tuesday s– 10:15 a.m. (Civil Eng.) 3. Tuesdays – 2:15 p.m. (Civil Eng.)4. Wednesdays – 2:15 p.m. (Civil Eng.)5. Thursdays – 2:15 p.m. (Civil Eng.)

NB: Groups 1 & 2 are presenting on Friday September 23, 2011.

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Assessments:

Individual Assignment: 1st Oral Quizz on Friday September 30, 2011.

a) Heat – 2.5 %

NB: This will be conducted in my office (Room E 18). Students will indicate a topic of their choice which they would be quizzed on.

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Assessments Cont’d:

Tutorial Groups are Assignment Groups:

1. Mondays – 12:15 p.m. (Mechanical Eng.)2. Tuesday s– 10:15 a.m. (Civil Eng.) 3. Tuesdays – 2:15 p.m. (Civil Eng.)4. Wednesdays – 2:15 p.m. (Civil Eng.)5. Thursdays – 2:15 p.m. (Civil Eng.)

NB: Groups 3 to 5 would be quizzed on Friday September 30, 2011.

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Assessments Cont’d:

Tutorial Groups are Assignment Groups:

1. Mondays – 12:15 p.m. (Mechanical Eng.)

2. Tuesday s– 10:15 a.m. (Civil Eng.) 3. Tuesdays – 2:15 p.m. (Civil Eng.)4. Wednesdays – 2:15 p.m. (Civil Eng.)5. Thursdays – 2:15 p.m. (Civil Eng.)

NB: Groups 1 to 2 would be quizzed on Friday October 7, 2011.

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1.5 The Gas Laws

Introduction:The experimental relationships between the pressures, volumes and temperatures of gases were investigated by various workers in the 17th and 18th centuries. These early experiments resulted in three laws – the so-called gas laws.

(A-Level Physics by Roger Muncaster, 4th Ed. Pg 249)

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1.5 The Gas Laws

1. Boyle’s Law: For a fixed mass of gas at constant temperature, the product of pressure and volume is a constant

2. Charles’ Law: For a fixed mass of gas at constant pressure, the volume is directly proportional to the temperature measured in Kelvin.

3. Pressure Law: For a fixed mass of gas at constant volume, the pressure is directly proportional to the temperature measured in Kelvin.

(A-Level Physics by Roger Muncaster, 4th Ed, pg 249)

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1.5 The Gas Laws

Kinetic Theory of Matter:

Physics for the IB Diploma by Tim Kirk, pg 24.

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1.5 The Gas Laws

Kinetic Theory of Matter: Solids

Physics for the IB Diploma by Tim Kirk, pg 24.

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1.5 The Gas Laws

Kinetic Theory of Matter: Liquids

Physics for the IB Diploma by Tim Kirk, pg 24.

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1.5 The Gas Laws

Kinetic Theory of Matter: Gases

Physics for the IB Diploma by Tim Kirk, pg 24.

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1.5 The Gas Laws

Kinetic Theory of Gases:Assumptions:1. Newtonian Mechanics applicable to molecules.2. No intermolecular forces present. 3. Molecules are perfectly spherical (point

objects).4. Infinitesimal size of molecules (no volume).5. Molecules in Random motion.6. Molecular collisions are elastic (K.E.

Conserved).7. Duration of molecular collisions is negligible. Taken from Physics for the IB Diploma by Tim Kirk, pg

29.

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1.5 The Gas Laws

Boyle’s Law: For a fixed mass of gas at constant temperature, the pressure of a gas is inversely proportional to its volume.

.),(1 constTmV

P ConstVPVPVP 332211

Robert Boyle: Considered a founder of the scientific method, 17th-century English scientist Robert Boyle believed in the importance of objective observation and controlled experimentation. He separated chemistry from alchemy and was the first to isolate and study a gas. Microsoft ® Encarta ® 2007

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1.5 The Gas Laws

Experimental Verification of Boyle’s Law:

(A-Level Physics by Roger Muncaster, 4th Ed. Pg 259)

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1.5 The Gas LawsExperimental Verification of Boyle’s Law Cont’d:

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1.5 The Gas Laws

Charles’ Law: For a fixed mass of gas at constant pressure, the volume is directly proportional to the temperature measured in Kelvin.

.),( constPmTV ConstTV

TV

TV

3

3

2

2

1

`1

Jacques Charles (1746-1823), French chemist, physicist, and aeronaut. Jacques Alexandre César Charles was born in Beaugency, Loiret. In 1783 he made the first balloon using hydrogen gas and ascended to a height of nearly 3 km (2 mi). In 1787 he discovered the relationship between the volume of gas and temperature, known variously as Gay-Lussac's law or Charles's law. He was elected to the French Academy in 1785. Microsoft ® Encarta ® 2007.

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1.5 The Gas Laws

Experimental Verification of Charles Law:

(A-Level Physics by Roger Muncaster, 4th Ed. Pg 259)

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2.4 The Gas LawsExperimental Verification of Charles Law Cont’d:

(A-Level Physics by Roger Muncaster, 4th Ed. Pg 259)

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1.5 The Gas Laws

Comparison of Boyle’s Law and Charles Law:

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1.5 The Gas Laws

Pressure Law: For a fixed mass of gas at constant volume, the pressure is directly proportional to the temperature measured in Kelvin.

NB: The Pressure Law may be derived from the previous two laws.

.),( constVmTP ConstTP

TP

TP

3

3

2

2

1

`1

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1.5 The Gas Laws

Experimental Verification of Pressure Law:

(A-Level Physics by Roger Muncaster, 4th Ed. Pg 260-1)

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1.5 The Gas LawsExperimental Verification of Pressure Law Cont’d:

(A-Level Physics by Roger Muncaster, 4th Ed. Pg 260-1)z

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1.5 The Gas Laws

Ideal Gas Equation: In this equation, n represents the number of moles of a gas. The constant R on the right-hand side of the equation is a universal constant and has a value of 8.31447 J/mol·K. This single equation can predict the behavior of a gas even if multiple conditions are changed simultaneously. If both the pressure and volume of a gas double, for example, its temperature will increase by a factor of four. Microsoft ® Encarta ® 2007

nRTPV

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1.5 The Gas Laws

Ideal Gas Equation:This is often referred to as an equation of state. It is employed to predict the behaviour of a system.

System:This is a region of space set aside for scientific investigation. The parameters pressure, volume and temperature gives quantitative description of this system and are deemed as thermodynamic quantities. Thus the ideal gas equation gives the relationship between pressure, volume and temperature of a gas.nRTPV

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1.5 The Gas Laws

Ideal Gas Equation Cont’d:By combining the three gas laws results:

1. Boyle’s Law:2. Charles’ Law:3. Pressure Law:The three quantities are thus related:

.),(1 constTmV

P

.),( constVmTP .),( constPmTV

.)( constmTPV

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1.5 The Gas Laws

Ideal Gas Equation Cont’d:Introducing a constant of proportionality results:

Thus the ideal gas equation gives the relationship between pressure, volume and temperature of a gas.

ConstTVP

TVP

TVP

3

33

2

22

1

1`1

nRTPV

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1.5 The Gas Laws

Ideal Gas Equation Cont’d:

Where:P – Pressure of a gas in Pa (Nm-2).V – Volume occupied by the gas in m3.T – Thermodynamic temperature of a gas in

K.n – Number of moles of a gas in mol.R – Universal gas constant = 8.314 J mol-1 K-1.

nRTPV

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Lecture Notes:

For this information, visit my website:

http://ugphysics.weebly.com

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END OF LECTURE