Free Essay

Force Convection

In: Science

Submitted By noreehan
Words 1571
Pages 7
LAB - RADIAL FLOW REACTION TURBINE

Objectives:

To measure volume flow rate, input head, hydraulic input power, torque, brake power & turbine efficiency when the brake force is increase

Theoretical Background:

Radial flow

When a fluid flows radially inwards or outwards from a centre, between two parallel planes as in Fig. 6.21, the streamlines will be radial straight lines and the streamtubes will be in forms of sectors. The area of flow will therefore increase as the radius increases, causing the velocity to decrease. Since the flow pattern is symmetrical, the total energy per unit weight H will be the same for all streamlines and for all points along each streamlines if we assume that there is no loss of energy.
[pic]

Figure 6.21
If v is the radial velocity and p is the pressure at any radius r,

H = p/ρg + v²/2g = constant …………………………(6.31)

Applying the continuity of flow equation flow and assuming that the density of the fluid remains constant, as would be the case for the fluid,

Volume rate of flow, Q = area x velocity = 2πrb x v

where b is the distance between the planes. Thus,

v = Q/2πrb

and substituting in equation………(6.31)

p/ρg + Q²/ 8π²r²b² = H p = ρg [ H – ( Q²/ 8π²b² ) x ( 1/r² )] …………………..(6.32)

If the pressure p at any radius r is plotted in Fig. 6.21(c), the curve will be parabolic and is sometimes referred to as Barlow’s curve.

If the flow discharges to the atmosphere at the periphery, the pressure at any points between the plates will be below atmospheric; there will be a force tending to bring the two plates together and so shut off flow. This phenomenon can be observed in a case of a disc valve. Radial flow under the disc will cause the disc to be drawn down onto the valve seating. This will cause the flow to stop, the pressure between the plates will return to atmospheric and the static pressure of the fluid on the upstream side of the disc will push it off its seating again. The disc will tend to vibrate on the seating and the flow will be to intermittent.

Flow in a curved path. Pressure gradient and change of total energy across the streamlines.

Velocity is a vector quantity with both magnitude and direction. When a fluid flows in a curved path, the velocity of the fluid along any streamline will undergo a change due to its change of direction, irrespective of any alteration in magnitude which may also occur. Considering the streamtube (shown in fig. 6.22),

[pic]

fig. 6.22:

as the fluid flows round the curved there will be a rate of change of velocity, that is to say an acceleration, towards the centre of curvature of the streamtube. The consequent rate of change of momentum of the fluid must be due, in accordance with Newton’s second law, to a force acting radially across the streamlines resulting from the difference of pressure between the sides BC and AD of the of the streamtube element.

In Fig. 4.2, suppose that the control volume ABCD subtends an angle δθ at the centre of curvature O, has length δs in the direction of flow and thickness b perpendicular to the diagram. For the streamline AD, let r be the radius of curvature, p the pressure and v the velocity of the fluid. For the streamline BC, the radius will be r + δr, the pressure p + δp and the velocity v + δv, where δp is the change of pressure in a radial direction.

From the velocity diagram,

Change of velocity in radial direction, δv = v δθ

Or since δθ = δs/r,

Radial change of velocity = v δs/r between AB and CD

Mass per unit time flowing = mass density x area x velocity through streamtube = ρ x ( b x δs ) x v

Change of momentum per unit = mass per unit time x radial change of time in radial direction velocity = ρbδrv² δs/r ………………………..…6.33

this rate of change of momentum is produced by the force due to the pressure difference between faces BC and AD of the control volume:

force = [(p + δp) – p ] bδs

equating equations (6.33) and (6.34), according to Newton’s second law,

δpbδs = ρbδrv²δs/r δp/δr = ρv²/r

for an incompressible fluid, ρ will be constant and equation (6.35) can be expressed in the of the pressure head h. since p = ρgh, we have δp = ρgδh.
Substituting in equation (6.35),

pg δh/δr = ρv²/r, δh/δr = v²/gr,

or, in the limit as δr tends to zero,

rate of change of pressure head in radial direction

= dh/dr = v²/gr ……………………………………(6.36)

to produce the curve flow shown in Fig. 6.22, we have seen that there must be a change of pressure head in a radial direction. However, since the velocity v along the streamline AD is different from the velocity v + δv along BC, there will also be a change in the velocity head from one streamline to another:

rate of change of velocity head radially:

= [(v + δv)² - v²] / 2gδr = v/g x δv/δr, neglecting products of small quantities, = v/g x δv/δr, as δr tends to zero. ……………….(6.37)

in streamlines are in a horizontal plane, so that changes changes in potential head do not occur, the change of total head H – i.e. the total energy per unit weight – in a radial direction, δH/δr, is given by,

δH/δr = change of pressure head + change of velocity head.

Substituting from equations (6.36) and (6.37), in the limit,

Change of total energy with radius, dH/dr = v²/gr + (v/g) x (dv/dr)

dH/dr = v²/gr + (v/g) x (dv/dr) ……………………(6.38)

the term (v/r + dv/dr) is also known as the vorticity of the fluid.
In obtaining equation 6.38, it has been assumed that the streamlines are horizontal, but this equation also applies to cases where the streamlines are inclined to the horizontal, since the fluid in the control volume is in effect weightless, being supported vertically by the surrounding fluid.

If the streamlines are straight lines, r = œ and dv/dr = 0. From equation (6.38) for a stream of fluid in which the velocity is uniform across the cross-section, and neglecting friction we have dH/dr = 0 and the total energy per unit weight H is constant for all points on all streamlines. This applies whether the streamlines are parallel or inclined, as the case of radial flow.

Procedures:

1) The model of the RADIAL FLOW REACTION TURBINE which is connected to the computer system is used to run the experiment. Lab assistant showed how to use the machine.
2) The machine is switched on; knob is used to adjust the brake force until we got the required steady value as shown on the monitor.
3) When the value of brake force is steady, the value of volume flow rate, input head, hydraulic input power, torque, brake power and turbine efficiency measured by computer will be taken.
4) The brake force is increased by adjusting the knob.
5) The procedures of 3 to 4 are repeated until we got the table of graph.
6) We can get the required value calculated by the computer automatically.

Sample of calculation:
Comparison tables:

Given: g = 9.81 m/s d = 0.09 m Cd = 0.63 r = 0.024m ρw = 998.2

Volume flow rate, Q v = Cd π d 2 √( 2 ρw d Po ) = (0.63) (π) (0.09)2 √(2(998.2)(34.5) 4πw 4 π (2 π (154.37)

= 0.000345 m3 s

Impact head, H1 = P1 = 243089 = 24.824m ρw g (998.2)(9.81)

Hydraulic Input Power, Ph = ρw g Qv H1 = (998.2) (9.81) (0.000345)(24.824) = 80.947 watt

Torque, T = Fb r = 0.44 x 0.024 = 0.01 Nm

Brake power,Pb = 2 π n = 2 π (154.37) (0.01) = 9.699 watt

Turbine efficiencies, Et(%) = Pb x 100 Ph = 9.699 x 100 80.947

= 11.98%

Discussion:

From our observation of the experiment result, it is found that the increasing of the break forces, Fb the rotational speed of turbine, Hz is also increase .The increasing of rotational speed of turbine caused by the increasing of the input head, Hi, slowly. The turbine efficiency, Et, is increase gradually. The hydraulic input Power, Ph , decrease gradually. The torque, T, of turbine is increase slowly. However the brake power, Pb , increase gradually and volume flow rate, Qv decrease slowly. All the data we get are from the computer. But from the theoretical calculation, we found small different value compared with computer data. We assume the error is come from sensor of equipments. As we know before, this equipment has some problem.

Conclusion:

From the experiment we can conclude that the rotational speed of turbine, Hz and the increase proportionally with brake power, Pb ,efficiency,Et, input head, Hi, and torque, T, but decreased proportionally with volume flow rate, Qv and hydraulic input power,Ph .The theoretical data has a small different value with the experimental value caused equipment error.

Reference:

1) Fluid Mechanics (4th edition), John F. Douglas, Janusz M. Gasiorek, John A. Swaffield, Prentice Hall 2001.

2) Fluid Mechanics (4th edition), Frank M. White, McGraw Hill International Edition.

Similar Documents

Premium Essay

Force Convection

...Title: Forced Convection Objective: To demonstrate the use of extended surface such as fin and pin to improve the heat transfer in forced convection. Introduction: Convection is the study of conduction in a fluid as enhanced by its "convective transport", that is, its velocity with respect to a solid surface. It thus combines the energy equation, or first law of thermodynamics, with the continuity and momentum relations of fluid mechanics. The causes of convection are generally described as one of either natural or forced. However the distinction between natural and forced convection is particularly important for convective heat transfer. Forced convection or also known as heat advection studies the heat transfer between a moving fluid and a solid surface. There are various types of forced convection, such as flow in a tube or across a flat plate and so on. In forced convection, the fluid has a nonzero streaming motion in the field away from the body surface, caused perhaps by a pump or fan or other driving force independent of the presence of the body. Also in this class are bodies moving through a still fluid, since fluid velocities are forced and may be large, heat transfer via forced convection will usually be significantly larger. It should be considered as one of the main methods of useful heat transfer as significant amounts of heat energy can be transported very efficiently and this mechanism is found very commonly in everyday life, including central heating,......

Words: 945 - Pages: 4

Premium Essay

Heat Transfer

...Conduction is most prevalent in solids but it can also be found in liquids and gases. The rate at which heat is transmitted through a material by conduction depends on thermal conductivity which is a characteristic of a material and its mass. The easiest way to think of conduction is to hold a metal rod by one end and put the other over a fire. Eventually the hot energetic molecules from the fire will transfer to the cold, less energetic molecules of the metal rod and slowly creep up the rod to the cold end where it is being held and then move to the hand and cause burns. The second method of heat transfer is convection which is the transfer of energy through a circulating gas or liquid to or from a solid object. An example of convection is a pot on the hot stove to the water inside which then heats up the pot and the that heats up the water. Convection consists of two energy transfer mechanisms. The first occurs...

Words: 568 - Pages: 3

Premium Essay

Heat Transfer and Its Applications

...transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species, either cold or hot, to achieve heat transfer. While these mechanisms have distinct characteristics, they often occur simultaneously in the same system. Heat conduction, also called diffusion, is the direct microscopic exchange of kinetic energy of particles through the boundary between two systems. When an object is at a different temperature from another body or its surroundings, heat flows so that the body and the surroundings reach the same temperature, at which point they are in thermal equilibrium. Such spontaneous heat transfer always occurs from a region of high temperature to another region of lower temperature, as described by the second law of thermodynamics. Heat convection occurs when bulk flow of a fluid (gas or liquid) carries heat along with the flow of matter in the fluid. The flow of fluid may be forced by external processes, or sometimes (in gravitational fields) by buoyancy forces caused when thermal energy expands the fluid (for example in a fire plume), thus influencing its own transfer. The latter process is often called "natural convection". All convective processes also move heat partly by diffusion, as well. Another form of convection is forced convection. In this case the fluid is forced to flow by use of a pump, fan or......

Words: 312 - Pages: 2

Free Essay

Mkt1

...Company G 3-Year Marketing Plan Assessment Code: Mkt1 Student Name: Rhonda Wilson Student ID: 000165977 Date: May 25, 2009 Mentor Name: Khirstin Hadley Table of Contents Introduction Error! Bookmark not defined. Mission Statement Error! Bookmark not defined. Market Objectives Error! Bookmark not defined. Target Market Error! Bookmark not defined. Product Objective Error! Bookmark not defined. Price Objective Error! Bookmark not defined. Place Objective Error! Bookmark not defined. Promotion Objective Error! Bookmark not defined. Competitive Situation Analysis Error! Bookmark not defined. Consumer Product Classification Error! Bookmark not defined. Analysis of Competition using Porter’s 5 Forces Model Error! Bookmark not defined. SWOT Analysis Error! Bookmark not defined. Strengths Error! Bookmark not defined. Weaknesses Error! Bookmark not defined. Opportunities Error! Bookmark not defined. Threats Error! Bookmark not defined. Marketing Strategies Error! Bookmark not defined. Product Strategies Error! Bookmark not defined. Price Strategies Error! Bookmark not defined. Place Strategies Error! Bookmark not defined. Promotion Strategies Error! Bookmark not defined. Tactics and Action Plan Error! Bookmark not defined. Product Action Plan 7 Price Action Plan 7 Place Action Plan 7 Promotion Action Plan 7 Monitoring Procedures Error! Bookmark not defined. Mission Statement: Our mission is to provide top......

Words: 2001 - Pages: 9

Free Essay

Marketing Plan

...Error! Bookmark not defined. Consumer Product Classification Error! Bookmark not defined. Analysis of Competition using Porter’s 5 Forces Model Error! Bookmark not defined. SWOT Analysis Error! Bookmark not defined. Strengths Error! Bookmark not defined. Weaknesses Error! Bookmark not defined. Opportunities Error! Bookmark not defined. Threats Error! Bookmark not defined. Marketing Strategies Error! Bookmark not defined. Product Strategies Error! Bookmark not defined. Price Strategies Error! Bookmark not defined. Place Strategies Error! Bookmark not defined. Promotion Strategies Error! Bookmark not defined. Tactics and Action Plan Error! Bookmark not defined. Product Action Plan 7 Price Action Plan 7 Place Action Plan 7 Promotion Action Plan 7 Monitoring Procedures Error! Bookmark not defined. Mission Statement: Our mission is to provide top quality appliances that will become the global brand of choice. Company G was established by top designers and engineers who are continuously innovating new appliances to keep up with our evolving market. Market Objectives: Target Market: We want to provide an oven that heats food just as fast as a microwave but provides tastier and healthier foods for our everyday families. We want to focus on working class families with children that want to provide healthier meals. Our convection oven will...

Words: 1986 - Pages: 8

Premium Essay

Rtrete

...No. Information on Every Subject 1. Unit Name: Physics I 2. Code: FHSP1014 3. Classification: Major 4. Credit Value: 4 5. Trimester/Year Offered: 1/1 6. Pre-requisite (if any): No 7. Mode of Delivery: Lecture, Tutorial, Practical 8. Assessment System and Breakdown of Marks: Continuous assessment: 50% - Theoretical Assessment (Tests/Quizzes/Case Studies) (30%) - Practical Assessment (Lab reports/Lab tests) (20%) Final Examination 9. 10. 50% Academic Staff Teaching Unit: Objective of Unit: The aims of this course are to enable students to: • appreciate the important role of physics in biology. • elucidate the basic principles in introductory physics enveloping mechanics, motion, properties of matter and heat. • resolve and interpret quantitative and qualitative problems in an analytical manner. • acquire an overall perspective of the inter-relationship between the various topics covered and their applications to the real world. • acquire laboratory skills including the proper handling and use of laboratory apparatus and materials. 11. Learning Outcome of Unit: At the end of the course, students will be able to: 1. Identify and practice the use of units and dimensional analysis, uncertainty significant figures and vectors analysis. 2. Apply and solve problems related to translational and rotational kinematics and dynamics in one and two dimensions. 3. Apply and solve problems related to......

Words: 765 - Pages: 4

Premium Essay

Physics

...No. Information on Every Subject 1. Unit Name: Physics I 2. Code: FHSP1014 3. Classification: Major 4. Credit Value: 4 5. Trimester/Year Offered: 1/1 6. Pre-requisite (if any): No 7. Mode of Delivery: Lecture, Tutorial, Practical 8. Assessment System and Breakdown of Marks: Continuous assessment: 50% - Theoretical Assessment (Tests/Quizzes/Case Studies) (30%) - Practical Assessment (Lab reports/Lab tests) (20%) Final Examination 9. 10. 50% Academic Staff Teaching Unit: Objective of Unit: The aims of this course are to enable students to: • appreciate the important role of physics in biology. • elucidate the basic principles in introductory physics enveloping mechanics, motion, properties of matter and heat. • resolve and interpret quantitative and qualitative problems in an analytical manner. • acquire an overall perspective of the inter-relationship between the various topics covered and their applications to the real world. • acquire laboratory skills including the proper handling and use of laboratory apparatus and materials. 11. Learning Outcome of Unit: At the end of the course, students will be able to: 1. Identify and practice the use of units and dimensional analysis, uncertainty significant figures and vectors analysis. 2. Apply and solve problems related to translational and rotational kinematics and dynamics in one and two dimensions. 3. Apply and solve problems related to......

Words: 765 - Pages: 4

Free Essay

None

...Buoyancy is an upward force exerted by a fluid that opposes the weight of an immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the column than at the top. This difference in pressure results in a net force that tends to accelerate an object upwards. Explanation: The ability or tendency to float in water or other fluid. The power of a liquid to keep something afloat. http://en.wikipedia.org/wiki/Buoyancy Archimedes' principle indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces. Archimedes' principle is a law of physics fundamental to fluid mechanics. Archimedes of Syracuse[1] formulated this principle, which bears his name. Explanation: The weight of the displaced fluid is directly proportional to the volume of the displaced fluid. Thus, among objects with equal masses, the one with greater volume has greater buoyancy. http://en.wikipedia.org/wiki/Archimede’s Principle Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water......

Words: 1014 - Pages: 5

Premium Essay

Past Paper

...GCSE Physics Revision notes 2014 Contents Static and Current Electricity .............................................................................................................. 2 Properties of Waves ........................................................................................................................... 12 Uses of Waves..................................................................................................................................... 13 Forces, Moments and Pressure......................................................................................................... 14 Energy Transfers................................................................................................................................. 17 Energy Calculations ............................................................................................................................ 20 Radioactivity ........................................................................................................................................ 22 Magnetism and Electromagnetism ................................................................................................... 24 Space .................................................................................................................................................... 27 These notes cover the main areas of this subject. Please check the specific areas you need with your exam board. They......

Words: 6048 - Pages: 25

Premium Essay

Physics Graph

...1) When is the average velocity of an object equal to the instantaneous velocity? A) always B) never C) only when the velocity is constant D) only when the velocity is increasing at a constant rate 2) A new car manufacturer advertises that their car can go "from zero to sixty in 8 s". This is a description of A) average speed. B) instantaneous speed. C) average acceleration. D) instantaneous acceleration. 3) Suppose that a car traveling to the East (+x direction) begins to slow down as it approaches a traffic light. Make a statement concerning its acceleration. A) The car is decelerating, and its acceleration is positive. B) The car is decelerating, and its acceleration is negative. C) The acceleration is zero. D) A statement cannot be made using the information given. 4) Suppose that a car traveling to the West (-x direction) begins to slow down as it approaches a traffic light. Make a statement concerning its acceleration. A) The car is decelerating, and its acceleration is positive. B) The car is decelerating, and its acceleration is negative. C) The acceleration is zero. D) A statement cannot be made using the information given. 5) Suppose that an object is moving with a constant velocity. Make a statement concerning its acceleration. A) The acceleration must be constantly increasing. B) The acceleration must be constantly decreasing. C) The acceleration must be a constant non-zero value. D) The acceleration must be equal to......

Words: 10622 - Pages: 43

Premium Essay

Gravitainal Lab

...activities where physics is applied. Skating is a type of movement that is made possible through the laws of motion found in physics. Skating can help explain the term movement, what makes skaters move and what keeps skaters moving while in motion. Also, it helps explain what it takes to stop moving or turn the process of moving in another direction. Skating can also reveal the concept of acceleration and deceleration, as well as the concept of speed. While putting a skate, nothing will happen to such a person unless an external force acts on him or her. The concept of inertia states that a body in motion will always tend to move while a body at rest will always tend to rest unless an external force acts on it (Laws, Sugano, and Swope, 2002). This is the first thing that happens before a person starts skating. The skater will always remain at rest until he applies some force to start moving. While on motion, the skater will tend to move unless he applies a force to stop. This is also an explanation of Newton’s first law of motion which states that every object or body in a state of uniform movement will tend to remain in...

Words: 1822 - Pages: 8

Free Essay

Physics

...*Physics Prelims (1-7).qxd 12/11/08 1:00 PM Page 1 SCIENCE VISUAL RESOURCES PHYSICS An Illustrated Guide to Science The Diagram Group *Physics Prelims (1-7).qxd 12/11/08 1:00 PM Page 2 Physics: An Illustrated Guide to Science Copyright © 2006 The Diagram Group Author: Derek McMonagle BSc PhD CSci CChem FRSC Editors: Catherine Gaunt, Jamie Stokes Design: Anthony Atherton, Richard Hummerstone, Lee Lawrence, Tim Noel-Johnson, Phil Richardson Illustration: Peter Wilkinson Picture research: Neil McKenna Indexer: Martin Hargreaves All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For information contact: Chelsea House An imprint of Infobase Publishing 132 West 31st Street New York NY 10001 For Library of Congress Cataloging-in-Publication Data, please contact the Publisher ISBN 0-8160-6167-X Chelsea House books are available at special discounts when purchased in bulk quantities for businesses, associations, institutions, or sales promotions. Please call our Special Sales Department in New York at 212/967-8800 or 800/322-8755. You can find Chelsea House on the World Wide Web at http://www.chelseahouse.com Printed in China CP Diagram 10 9 8 7 6 5 4 3 2 This book is printed on acid-free paper. *Physics Prelims (1-7).qxd 12/11/08 1:00 PM Page...

Words: 78462 - Pages: 314

Free Essay

Physics

...SENIOR SECONDARY COURSE PHYSICS 1 (CORE MODULES) Coordinators Dr. Oum Prakash Sharma Sh. R.S. Dass NATIONAL INSTITUTE OF OPEN SCHOOLING A-25, INSTITUTIONAL AREA, SECTOR-62, NOIDA-201301 (UP) COURSE DESIGN COMMITTEE CHAIRMAN Prof. S.C. Garg Former Pro-Vice Chancellor IGNOU, Maidan Garhi, Delhi MEMBERS Prof. A.R. Verma Former Director, National Physical Laboratory, Delhi, 160, Deepali Enclave Pitampura, Delhi-34 Dr. Naresh Kumar Reader (Rtd.) Deptt. of Physics Hindu College, D.U. Dr. Oum Prakash Sharma Asstt. Director (Academic) NIOS, Delhi Prof. L.S. Kothari Prof. of Physics (Retd.) Delhi University 71, Vaishali, Delhi-11008 Dr. Vajayshree Prof. of Physics IGNOU, Maidan Garhi Delhi Sh. R.S. Dass Vice Principal (Rtd.) BRMVB, Sr. Sec. School Lajpat Nagar, New Delhi-110024 Dr. G.S. Singh Prof. of Physics IIT Roorkee Sh. K.S. Upadhyaya Principal Jawahar Navodaya Vidyalaya Rohilla Mohammadabad (U.P.) Dr. V.B. Bhatia Prof. of Physics (Retd.) Delhi University 215, Sector-21, Faridabad COURSE DEVELOPMENT TEAM CHAIRMAN Prof. S.C. Garg Former Pro-Vice Chancellor IGNOU, Delhi MEMBERS Prof. V.B. Bhatia 215, Sector-21, Faridabad Prof. B.B. Tripathi Prof. of Physics (Retd.), IIT Delhi 9-A, Awadhpuri, Sarvodaya Nagar Lucknow-226016 Sh. K.S. Upadhyaya Principal Navodaya Vidyalaya Rohilla Mohammadabad, (U.P.) Dr. V.P. Shrivastava Reader (Physics) D.E.S.M., NCERT, Delhi EDITORS TEAM CHAIRMAN Prof. S.C. Garg Former Pro-Vice Chancellor IGNOU, Delhi MEMBERS Prof. B.B.......

Words: 131353 - Pages: 526

Premium Essay

Answers to Conceptual Sciences

...Answers to Conceptual Integrated Science End-of-Chapter Questions Chapter 1: About Science Answers to Chapter 1 Review Questions 1 The era of modern science in the 16th century was launched when Galileo Galilei revived the Copernican view of the heliocentric universe, using experiments to study nature’s behavior. 2 In Conceptual Integrated Science, we believe that focusing on math too early is a poor substitute forconcepts. 3 We mean that it must be capable of being proved wrong. 4 Nonscientific hypotheses may be perfectly reasonable; they are nonscientific only because they are not falsifiable—there is no test for possible wrongness. 5 Galileo showed the falseness of Aristotle’s claim with a single experiment—dropping heavy and lightobjects from the Leaning Tower of Pisa. 6 A scientific fact is something that competent observers can observe and agree to be true; a hypothesis is an explanation or answer that is capable of being proved wrong; a law is a hypothesis that has been tested over and over and not contradicted; a theory is a synthesis of facts and well-tested hypotheses. 7 In everyday speech, a theory is the same as a hypothesis—a statement that hasn’t been tested. 8 Theories grow stronger and more precise as they evolve to include new information. 9 The term supernatural literally means “above nature.” Science works within nature, not above it. 10 They rely on subjective personal experience and do not lead to testable hypotheses. They lie outside...

Words: 81827 - Pages: 328

Free Essay

Biology

.... .1 Chapter 2: Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 Chapter 3: Atoms, Elements, and the Periodic Table . . . . . . . . . .9 Chapter 4: States of Matter . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Chapter 5: Matter—Properties and Changes . . . . . . . . . . . . . . .17 Chapter 6: Atomic Structure and Chemical Bonds. . . . . . . . . . .21 Chapter 7: Chemical Reactions. . . . . . . . . . . . . . . . . . . . . . . . .23 Chapter 8: Substances, Mixtures, and Solubility . . . . . . . . . . . .25 Chapter 9: Carbon Chemistry . . . . . . . . . . . . . . . . . . . . . . . . .29 Chapter 10: Motion and Momentum . . . . . . . . . . . . . . . . . . . .33 Chapter 11: Force and Newton’s Laws . . . . . . . . . . . . . . . . . . .37 Chapter 12: Forces and Fluids . . . . . . . . . . . . . . . . . . . . . . . . .41 Chapter 13: Energy and Energy Resources . . . . . . . . . . . . . . . .45 Chapter 14: Work and Simple Machines . . . . . . . . . . . . . . . . . .49 Chapter 15: Thermal Energy . . . . . . . . . . . . . . . . . . . . . . . . . .53 Chapter 16: Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 Chapter 17: Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....

Words: 14374 - Pages: 58