DOCSLIB.ORG

Force and Weight

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Force and Weight 5/19/14 Objectives Force and • Explain the difference between weight and mass. weight • Calculate weight from mass or mass from weight. Assessment Assessment 1. If you take a trip from Earth to the Moon, which statement 2. What is the weight of this below is correct? dumbbell, in newtons? A. Your mass and weight both decrease. B. Your mass stays the same and your weight decreases. 3. A person weighs 150 lbs. What is this weight in newtons? C. Your mass decreases and your weight stays the same. What is this person’s mass in D. Your mass increases and your weight decreases. kilograms? A 10 kg dumbbell resting on a table is partly supported by a spring that pulls upward with a force of 50 N. Physics terms Equations • mass • force Weight is mass multiplied by the strength of gravity. • weight • newtons At Earth’ s surface the strength of • pounds gravity is 9.8 newtons per kilogram. 1 5/19/14 Explaining motion What is mass? Isaac Newton was the first All matter has mass and takes person to explain WHY objects up space. move the way they do. A solid rock has mass. So do He based his laws of motion gases and liquids. on two key concepts: With your hand out the window • mass of a moving car, you feel the mass in the air pushing against • force you. Measuring mass What is force? The concept of force: The SI unit for mass is the kilogram. A force is a push or a pull. This object has a mass of 2 kilograms. What is force? Types of forces The concept of force: The concept of force: A force is a push or a pull. A force is a push or a pull. Forces can cause an object Forces can cause an object to change its motion. to change its motion. Examples of forces: Can you give some Can you give some • weight examples of forces? examples of forces? • friction • tension from rope • force from a spring • electric force 2 5/19/14 Units of force Units of force Quantitative: Force is measured in newtons. Weight is a type of force Weight vs. mass Mass is an intrinsic property that measures Weight is the force of gravity the quantity of matter in an object. acting on objects with mass. • Your mass does NOT change if you go into space. How is weight different from mass? Weight vs. mass Weight vs. mass Mass is an intrinsic property that measures Mass is a scalar quantity. the quantity of matter in an object. It has a magnitude (such as 60 kg), but no direction. • Your mass does NOT change if you go into space. Weight is a vector. It has magnitude AND direction. Weight is an extrinsic property that For objects on Earth, it always depends on the gravity force. points straight down toward the F w center of the Earth. • Your weight changes if you go into space. Your weight depends on your location. 3 5/19/14 Weight Weight Weight is the force of gravity acting One kilogram of mass weighs 9.8 N. 1 kg on objects with mass. This is roughly the mass and weight of a one liter water bottle. Weight is mass multiplied by the strength of gravity. At Earth’s surface the strength of gravity is 9.8 newtons per kilogram. Weight Weight One kilogram of mass weighs 9.8 N. 1 kg One kilogram of mass weighs 9.8 N. 1 kg This is roughly the mass and weight This is roughly the mass and weight of a one liter water bottle. of a one liter water bottle. Force is a vector, so it has a direction. What changes if you bring this bottle to the Moon? Fw = 9.8 N Fw = 9.8 N The force of weight always points straight down. Weight What is a pound? One kilogram of mass weighs 9.8 N. 1 kg The pound is the English unit of force. This is roughly the mass and weight of a one liter water bottle. The person standing on this scale is pushing down on it with a force of 125 pounds. What changes if you bring this bottle to the Moon? Fw = 1.6 N 4 5/19/14 What is a pound? Example problem The pound is the English unit of force. If a person has a weight of 125 pounds, what is her mass in kilograms? Pounds are a unit of force, not mass. One pound = 4.448 N The newton is a smaller unit of force than the pound. One newton = 0.225 lbs (~3.6 ounces) Convert to SI units Calculate the mass If a person has a weight of 125 pounds, Mass is weight divided by g. what is her mass in kilograms? Weight and mass Exploring the ideas Whenever you know the mass of an object, you Click this can calculate its weight. interactive calculator on page 135 Whenever you know the weight of an object, you can calculate its mass. 5 5/19/14 Engaging with the concepts Assessment Use the weight calculator to check 1. If you take a trip from Earth to the Moon, which statement your work when solving problems on below is correct? the student assignment. A. Your mass and weight both decrease. B. Your mass stays the same and your weight decreases. C. Your mass decreases and your weight stays the same. D. Your mass increases and your weight decreases. Assessment Assessment 1. If you take a trip from Earth to the Moon, which statement 2. What is the weight of this below is correct? dumbbell, in newtons? A. Your mass and weight both decrease. B. Your mass stays the same and your weight decreases. C. Your mass decreases and your weight stays the same. D. Your mass increases and your weight decreases. A 10 kg dumbbell is resting on a table partly supported by a spring that pulls upward with a force of 50 N. Assessment Assessment 2. What is the weight of this 3. A person weighs 150 lbs. dumbbell, in newtons? What is this weight in newtons? Fw = mg = (10 kg)(9.8 N/kg) = 98 N What is this person’s mass, in kilograms? 98 N 6 5/19/14 Assessment Assessment 3. A person weighs 150 lbs. 3. A person weighs 150 lbs. What is this weight in newtons? What is this weight in newtons? What is this person’s mass, in kilograms? What is this person’s mass, in kilograms? 7 .
Load more

Recommended publications
  • 5 Military Rucking Rules Every Backpacker Should Know 1. One
    5 Military Rucking Rules Every Backpacker Should Know The military has spent years studying the best way to move under a load (aka “rucking”). Here are 5 military rucking rules that translate well to hikers. “Rucking” is the military term for hiking under load. As you can imagine, this is a huge issue for the military, as soldiers must wear body armor and carry weapons, ammo, water, communications equipment, and other gear as they conduct patrols and missions. Rucking performance and injury prevention are hugely important for military operations and personnel. Movement over ground under load is also a key for hiking and backpacking. In reviewing the research the military has already done on this subject, we discovered five rules. Read on to make sure you’re following these military rucking rules on your next backcountry adventure. 1. One pound on your feet equals five pounds on your back. This old backpacking thumb rule holds true, according to a 1984 study from the U.S. Army Research Institute. They tested how much more energy was expended with different footwear (boots and shoes) and concluded that it take 4.7 to 6.4 times as much energy to move at a given pace when weight is carried on the shoe versus on the torso. In practical terms, this means you could carry half a gallon more of water (a little over 4 pounds) if you buy boots that are a pound lighter, which isn’t hard to do; and that’s a lot of water. Now imagine the energy savings of backpacking in light trail running shoes rather than heavy, leather backpacking boots over the course of 7- day backpacking trip.
    [Show full text]
  • Conversion Factor Table Copyright © by Jon Wittwer
    Conversion Factor Table http://www.et.byu.edu/~jww8 Copyright © by Jon Wittwer Multiple by To Get hp 2544.5 Btu / hr m / s 3.60 km / h inch 2.54 cm hp 745.70 W (watt) m / s 3.2808 ft / s This can also be written as: 1 inch = 2.54 cm hp 0.74570 kW m / s 2.237 mi / h (mph) A acre 43,560 ft2 hp 33,000 ft·lbf / min m / s2 3.2808 ft / s2 ampere·hr (A·h) 3,600 coulomb (C) hp 550 ft·lbf / sec metric ton 1000 kg hp·hr 2544 Btu ångström (Å) 1x10-10 m mil 0.001 in 6 atm (atmosphere) 1.01325 bar hp·hr 1.98x10 ft·lbf mi (mile) 5280 ft atm, std 76.0 cm of Hg hp·hr 2.68x106 J mi 1.6093 km atm, std 760 mm of Hg at 0ºC in 2.54* cm mi2 (square mile) 640 acres atm, std 33.90 ft of water in of Hg 0.0334 atm mph (mile/hour) 1.6093 km / hr atm, std 29.92 in of Hg at 30ºF in of Hg 13.60 in of water mph 88.0 ft / min (fpm) atm, std 14.696 lbf/in2 abs (psia) in of Hg 3.387 kPa mph 1.467 ft / s atm, std 101.325 kPa in of water 0.0736 in of Hg mph 0.4470 m / s 2 -6 atm, std 1.013x105 Pa in of water 0.0361 lbf / in (psi) micron 1x10 m in of water 0.002458 atm -3 atm, std 1.03323 kgf / cm2 mm of Hg 1.316x10 atm -4 atm, std 14.696 psia J J (joule) 9.4782x10 Btu mm of Hg 0.1333 kPa B bar 0.9869 atm, std J 6.2415x1018 eV mm of water 9.678x10-5 atm bar 1x105 Pa J 0.73756 ft·lbf N N (newton) 1 kg·m / s2 J1N·m Btu 778.169 ft·lbf N 1x105 dyne 7 Btu 1055.056 J J 1x10 ergs µN (microN) 0.1 dyne Btu 5.40395 psia·ft3 J / s 1 W N 0.22481 lbf K kg (kilogram) 2.2046226 lbm (pound mass) Btu 2.928x10-4 kWh N·m 0.7376 ft·lbf -5 kg 0.068522 slug N·m 1 J Btu 1x10 therm -3 kg 1x10 metric
    [Show full text]
  • An Atomic Physics Perspective on the New Kilogram Defined by Planck's Constant
    An atomic physics perspective on the new kilogram defined by Planck’s constant (Wolfgang Ketterle and Alan O. Jamison, MIT) (Manuscript submitted to Physics Today) On May 20, the kilogram will no longer be defined by the artefact in Paris, but through the definition1 of Planck’s constant h=6.626 070 15*10-34 kg m2/s. This is the result of advances in metrology: The best two measurements of h, the Watt balance and the silicon spheres, have now reached an accuracy similar to the mass drift of the ur-kilogram in Paris over 130 years. At this point, the General Conference on Weights and Measures decided to use the precisely measured numerical value of h as the definition of h, which then defines the unit of the kilogram. But how can we now explain in simple terms what exactly one kilogram is? How do fixed numerical values of h, the speed of light c and the Cs hyperfine frequency νCs define the kilogram? In this article we give a simple conceptual picture of the new kilogram and relate it to the practical realizations of the kilogram. A similar change occurred in 1983 for the definition of the meter when the speed of light was defined to be 299 792 458 m/s. Since the second was the time required for 9 192 631 770 oscillations of hyperfine radiation from a cesium atom, defining the speed of light defined the meter as the distance travelled by light in 1/9192631770 of a second, or equivalently, as 9192631770/299792458 times the wavelength of the cesium hyperfine radiation.
    [Show full text]
  • Guide for the Use of the International System of Units (SI)
    Guide for the Use of the International System of Units (SI) m kg s cd SI mol K A NIST Special Publication 811 2008 Edition Ambler Thompson and Barry N. Taylor NIST Special Publication 811 2008 Edition Guide for the Use of the International System of Units (SI) Ambler Thompson Technology Services and Barry N. Taylor Physics Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 (Supersedes NIST Special Publication 811, 1995 Edition, April 1995) March 2008 U.S. Department of Commerce Carlos M. Gutierrez, Secretary National Institute of Standards and Technology James M. Turner, Acting Director National Institute of Standards and Technology Special Publication 811, 2008 Edition (Supersedes NIST Special Publication 811, April 1995 Edition) Natl. Inst. Stand. Technol. Spec. Publ. 811, 2008 Ed., 85 pages (March 2008; 2nd printing November 2008) CODEN: NSPUE3 Note on 2nd printing: This 2nd printing dated November 2008 of NIST SP811 corrects a number of minor typographical errors present in the 1st printing dated March 2008. Guide for the Use of the International System of Units (SI) Preface The International System of Units, universally abbreviated SI (from the French Le Système International d’Unités), is the modern metric system of measurement. Long the dominant measurement system used in science, the SI is becoming the dominant measurement system used in international commerce. The Omnibus Trade and Competitiveness Act of August 1988 [Public Law (PL) 100-418] changed the name of the National Bureau of Standards (NBS) to the National Institute of Standards and Technology (NIST) and gave to NIST the added task of helping U.S.
    [Show full text]
  • Multidisciplinary Design Project Engineering Dictionary Version 0.0.2
    Multidisciplinary Design Project Engineering Dictionary Version 0.0.2 February 15, 2006 . DRAFT Cambridge-MIT Institute Multidisciplinary Design Project This Dictionary/Glossary of Engineering terms has been compiled to compliment the work developed as part of the Multi-disciplinary Design Project (MDP), which is a programme to develop teaching material and kits to aid the running of mechtronics projects in Universities and Schools. The project is being carried out with support from the Cambridge-MIT Institute undergraduate teaching programe. For more information about the project please visit the MDP website at http://www-mdp.eng.cam.ac.uk or contact Dr. Peter Long Prof. Alex Slocum Cambridge University Engineering Department Massachusetts Institute of Technology Trumpington Street, 77 Massachusetts Ave. Cambridge. Cambridge MA 02139-4307 CB2 1PZ. USA e-mail: [email protected] e-mail: [email protected] tel: +44 (0) 1223 332779 tel: +1 617 253 0012 For information about the CMI initiative please see Cambridge-MIT Institute website :- http://www.cambridge-mit.org CMI CMI, University of Cambridge Massachusetts Institute of Technology 10 Miller’s Yard, 77 Massachusetts Ave. Mill Lane, Cambridge MA 02139-4307 Cambridge. CB2 1RQ. USA tel: +44 (0) 1223 327207 tel. +1 617 253 7732 fax: +44 (0) 1223 765891 fax. +1 617 258 8539 . DRAFT 2 CMI-MDP Programme 1 Introduction This dictionary/glossary has not been developed as a definative work but as a useful reference book for engi- neering students to search when looking for the meaning of a word/phrase. It has been compiled from a number of existing glossaries together with a number of local additions.
    [Show full text]
  • Measuring in Metric Units BEFORE Now WHY? You Used Metric Units
    Measuring in Metric Units BEFORE Now WHY? You used metric units. You’ll measure and estimate So you can estimate the mass using metric units. of a bike, as in Ex. 20. Themetric system is a decimal system of measurement. The metric Word Watch system has units for length, mass, and capacity. metric system, p. 80 Length Themeter (m) is the basic unit of length in the metric system. length: meter, millimeter, centimeter, kilometer, Three other metric units of length are themillimeter (mm) , p. 80 centimeter (cm) , andkilometer (km) . mass: gram, milligram, kilogram, p. 81 You can use the following benchmarks to estimate length. capacity: liter, milliliter, kiloliter, p. 82 1 millimeter 1 centimeter 1 meter thickness of width of a large height of the a dime paper clip back of a chair 1 kilometer combined length of 9 football fields EXAMPLE 1 Using Metric Units of Length Estimate the length of the bandage by imagining paper clips laid next to it. Then measure the bandage with a metric ruler to check your estimate. 1 Estimate using paper clips. About 5 large paper clips fit next to the bandage, so it is about 5 centimeters long. ch O at ut! W 2 Measure using a ruler. A typical metric ruler allows you to measure Each centimeter is divided only to the nearest tenth of into tenths, so the bandage cm 12345 a centimeter. is 4.8 centimeters long. 80 Chapter 2 Decimal Operations Mass Mass is the amount of matter that an object has. The gram (g) is the basic metric unit of mass.
    [Show full text]
  • The Kibble Balance and the Kilogram
    C. R. Physique 20 (2019) 55–63 Contents lists available at ScienceDirect Comptes Rendus Physique www.sciencedirect.com The new International System of Units / Le nouveau Système international d’unités The Kibble balance and the kilogram La balance de Kibble et le kilogramme ∗ Stephan Schlamminger , Darine Haddad NIST, 100 Bureau Drive, Gaithersburg, MD 20899, USA a r t i c l e i n f o a b s t r a c t Article history: Dr. Bryan Kibble invented the watt balance in 1975 to improve the realization of the unit Available online 25 March 2019 for electrical current, the ampere. With the discovery of the Quantum Hall effect in 1980 by Dr. Klaus von Klitzing and in conjunction with the previously predicted Josephson effect, Keywords: this mechanical apparatus could be used to measure the Planck constant h. Following a Unit of mass proposal by Quinn, Mills, Williams, Taylor, and Mohr, the Kibble balance can be used to Kilogram Planck constant realize the unit of mass, the kilogram, by fixing the numerical value of Planck’s constant. Kibble balance In 2017, the watt balance was renamed to the Kibble balance to honor the inventor, who Revised SI passed in 2016. This article explains the Kibble balance, its role in the redefinition of the Josephson effect unit of mass, and attempts an outlook of the future. Quantum Hall effect Published by Elsevier Masson SAS on behalf of Académie des sciences. This is an open access article under the CC BY-NC-ND license Mots-clés : (http://creativecommons.org/licenses/by-nc-nd/4.0/).
    [Show full text]
  • Student Academic Learning Services Pounds Mass and Pounds Force
    Student Academic Learning Services Page 1 of 3 Pounds Mass and Pounds Force One of the greatest sources of confusion in the Imperial (or U.S. Customary) system of measurement is that both mass and force are measured using the same unit, the pound. The differentiate between the two, we call one type of pound the pound-mass (lbm) and the other the pound-force (lbf). Distinguishing between the two, and knowing how to use them in calculations is very important in using and understanding the Imperial system. Definition of Mass The concept of mass is a little difficult to pin down, but basically you can think of the mass of an object as the amount of matter contain within it. In the S.I., mass is measured in kilograms. The kilogram is a fundamental unit of measure that does not come from any other unit of measure.1 Definition of the Pound-mass The pound mass (abbreviated as lbm or just lb) is also a fundamental unit within the Imperial system. It is equal to exactly 0.45359237 kilograms by definition. 1 lbm 0.45359237 kg Definition of Force≡ Force is an action exerted upon an object that causes it to accelerate. In the S.I., force is measured using Newtons. A Newton is defined as the force required to accelerate a 1 kg object at a rate of 1 m/s2. 1 N 1 kg m/s2 Definition of ≡the Pound∙ -force The pound-force (lbf) is defined a bit differently than the Newton. One pound-force is defined as the force required to accelerate an object with a mass of 1 pound-mass at a rate of 32.174 ft/s2.
    [Show full text]
  • Weights and Measures Standards of the United States—A Brief History (1963), by Lewis V
    WEIGHTS and MEASURES STANDARDS OF THE UMIT a brief history U.S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS NBS Special Publication 447 WEIGHTS and MEASURES STANDARDS OF THE TP ii 2ri\ ii iEa <2 ^r/V C II llinCAM NBS Special Publication 447 Originally Issued October 1963 Updated March 1976 For sale by the Superintendent of Documents, U.S. Government Printing Office Wash., D.C. 20402. Price $1; (Add 25 percent additional for other than U.S. mailing). Stock No. 003-003-01654-3 Library of Congress Catalog Card Number: 76-600055 Foreword "Weights and Measures," said John Quincy Adams in 1821, "may be ranked among the necessaries of life to every individual of human society." That sentiment, so appropriate to the agrarian past, is even more appropriate to the technology and commerce of today. The order that we enjoy, the confidence we place in weighing and measuring, is in large part due to the measure- ment standards that have been established. This publication, a reprinting and updating of an earlier publication, provides detailed information on the origin of our standards for mass and length. Ernest Ambler Acting Director iii Preface to 1976 Edition Two publications of the National Bureau of Standards, now out of print, that deal with weights and measures have had widespread use and are still in demand. The publications are NBS Circular 593, The Federal Basis for Weights and Measures (1958), by Ralph W. Smith, and NBS Miscellaneous Publication 247, Weights and Measures Standards of the United States—a Brief History (1963), by Lewis V.
    [Show full text]
  • A) B) C) D) 1. Which Is an SI Unit for Work Done on an Object? A) Kg•M/S
    1. Which is an SI unit for work done on an object? 10. Which is an acceptable unit for impulse? A) B) A) N•m B) J/s C) J•s D) kg•m/s C) D) 11. Using dimensional analysis, show that the expression has the same units as acceleration. [Show all the 2. Which combination of fundamental units can be used to express energy? steps used to arrive at your answer.] A) kg•m/s B) kg•m2/s 12. Which quantity and unit are correctly paired? 2 2 2 C) kg•m/s D) kg•m /s A) 3. A joule is equivalent to a B) A) N•m B) N•s C) N/m D) N/s C) 4. A force of 1 newton is equivalent to 1 A) B) D) C) D) 13. Which two quantities are measured in the same units? 5. Which two quantities can be expressed using the same A) mechanical energy and heat units? B) energy and power A) energy and force C) momentum and work B) impulse and force D) work and power C) momentum and energy 14. Which is a derived unit? D) impulse and momentum A) meter B) second 6. Which pair of quantities can be expressed using the same C) kilogram D) Newton units? 15. Which combination of fundamental unit can be used to A) work and kinetic energy express the weight of an object? B) power and momentum A) kilogram/second C) impulse and potential energy B) kilogram•meter D) acceleration and weight C) kilogram•meter/second 7.
    [Show full text]
  • Foot–Pound–Second System
    Foot–pound–second system The foot–pound–second system or FPS system is a system of units built on three fundamental units: the foot for length, the (avoirdupois) pound for either mass or force (see below), and the second for time.[1] Contents Variants Pound as mass unit Pound-force as force unit Pound as force unit Other units Molar units Electromagnetic units Units of light Conversions See also References Variants Collectively, the variants of the FPS system were the most common system in technical publications in English until the middle of the 20th century.[1] Errors can be avoided and translation between the systems facilitated by labelling all physical quantities consistently with their units. Especially in the context of the FPS system this is sometimes known as the Stroud system after William Stroud, who popularized it.[2] Three approaches to English units of mass and force or weight[3][4] Base Force Weight Mass 2nd law of m = F F = W⋅a motion a g F = m⋅a System British Gravitational (BG) English Engineering (EE) Absolute English (AE) Acceleration ft/s2 ft/s2 ft/s2 (a) Mass (m) slug pound-mass pound Force (F), pound pound-force poundal weight (W) Pressure (p) pound per square inch pound-force per square inch poundal per square foot Pound as mass unit When the pound is used as a unit of mass, the core of the coherent system is similar and functionally equivalent to the corresponding subsets of the International System of Units (SI), using metre, kilogram and second (MKS), and the earlier centimetre–gram–second system of units (CGS).
    [Show full text]
  • The International System of Units (SI) - Conversion Factors For
    NIST Special Publication 1038 The International System of Units (SI) – Conversion Factors for General Use Kenneth Butcher Linda Crown Elizabeth J. Gentry Weights and Measures Division Technology Services NIST Special Publication 1038 The International System of Units (SI) - Conversion Factors for General Use Editors: Kenneth S. Butcher Linda D. Crown Elizabeth J. Gentry Weights and Measures Division Carol Hockert, Chief Weights and Measures Division Technology Services National Institute of Standards and Technology May 2006 U.S. Department of Commerce Carlo M. Gutierrez, Secretary Technology Administration Robert Cresanti, Under Secretary of Commerce for Technology National Institute of Standards and Technology William Jeffrey, Director Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. National Institute of Standards and Technology Special Publications 1038 Natl. Inst. Stand. Technol. Spec. Pub. 1038, 24 pages (May 2006) Available through NIST Weights and Measures Division STOP 2600 Gaithersburg, MD 20899-2600 Phone: (301) 975-4004 — Fax: (301) 926-0647 Internet: www.nist.gov/owm or www.nist.gov/metric TABLE OF CONTENTS FOREWORD.................................................................................................................................................................v
    [Show full text]