Forces are the pushes and pulls of our universe. This means you will need to find out how much the spring stretches for particular weights. This is your "zero" point.Add a known weight. Forcemeter Experiment. … FREE Shipping by Amazon . Standards. This neat little device can be built for almost nothing (I used plumbing off-cuts), but will let you measure pushes and pulls around you, as well as doing experiments with different-sized forces.It is perfect for kids still at school as well; it can be made by dads-and-lads together, or by competent older children alone, and it can be calibrated in Newtons and used to do home experiments to reinforce schoolwork (any UK readers with kids in Years 6 or 9, this will help them get ready for their SATs). So force meter is a fancy term for a scale here? We've found 148 phrases and idioms matching force meter. Homework on Force Meters. ), Participated in the The Instructables Book Contest. This activity is useful in classroom and home school environments. Read about 'Force meter for martial arts' on element14.com. Strictly speaking a "scale" measures mass/weight only in respect to the to pull of gravity. Forcemeter Experiment. The pedal force meter series 2.x for cars and HGVs measures forces acting on the foot pedal or the parking brake. Secondly, just to make sure: F = m * a -> Force (caused by the weight of an object) = mass (grams/pounds meassured value ect.) The students weigh the items and determine if their predictions are accurate. All you need to add is a slider that sticks to the scale. 5% coupon applied at checkout Save 5% with coupon. A fun one is to fire toy cars across the floor; how far will it travel when fired with a force of X Newtons? on Introduction. I few weeks ago I purchased a new Camaro with a Head's Up Display and among the data presented is a g-force meter. (Perhaps you would like to add a comment with ideas for other uses for this instructable? (I may still add a drop of glue to the knot, just to be sure.). $138.48 $ 138. To measure pulls, you need a hook or loop. Poke the hook of the paperclip through the smaller cardboard square. Add an object that weighs 1 Newton to the force meter. Force meters measure the weights of different masses. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. I have been keeping an eye out for a hydraulic cylinder that has a bore area of exactly of 1 square inch. Your meter is essentially finished, but you cannot yet actually measure any forces with it. The weight is the pull on the mass due to the local gravity-field (i.e. acceleration ({constant, g} gravity = 9.81m/s^2) Thus, 100g mass is pulled toward the earth by gravity with a force = 0.981N Finally, your design could used to measure the max static force required to move an object and overcome the force it's friction with a certain surface can support, from which static friction constants can be derived. You can use anything you want - hang a pound weight on there, draw a mark and call it pounds. Recalibration would be needed every time the bands are replaced. Make a mark on the tape where the bottom edge of the wider tube is. Force Meter. on Introduction. Annabeth Kaine began writing in 2010 with work appearing on various websites. Use metal washers to stop the rubber band slipping back out of the holes. I did only design the meter to be a short-life project anyway, to help Year Six kids (age 11) do extra work to support their SATs (UK version). How can a spring be used to measure a force? Continue measuring and marking for 2 through 5 Newtons. HOW TO – Make your own G-force meter. Hang a large piece of poster board on the wall. Add an object that weighs 1 Newton to the force meter. Regarding rubber bands, see step 6. There are two kinds of force gauges today: mechanical and digital force gauges. That is why the scale is drawn on tape - you can easily change or replace it when the band needs replacing. Your chosen units will depend on what you want to measure (the metric unit of force is the Newton), and what size thing you want to measure. You could even make up your own scale, based on any repeatable unit you want, but your results won't make as much sense to other people (although graphs etc would still be the same shape, so general conclusions could be reported). Turn the meter round, and (still holding the outer tube) you can use the inner tube to measure the force of a push, or to weigh something that won't hang on the loop, such as balls or eggs.You can also use the meter to investigate the effects of known forces, pushing or pulling until the meter reads a certain force and observing the effects. For the long term PVC pipe can be used to adapt a simple hardware store spring scale. Multiply … I'm busy with a project: a force meter so that martial artists can measure the power of their kicks and punches. add yourself a few extra rubber bands, a linear potentimeter, and a pull-up resistor and you got yourself a nice little force-controlled voltage splitter. Form the paper clip into a "hook" shape on one end. A force meter, also called a newton meter, is used to measure forces Forces can be contact forces, where objects must touch each other to exert a force. An everyday scale for measuring weight is a kind of force meter, but the term usually refers to the kind of device that takes advantages of Hooke's law for elastic materials, such as springs. Smile indeed! Put the narrow tube inside the wide tube, with the holes at the same end, and the outer holes lined up with two of the inner holes. Report a problem. This means you find out how much. Force Meters: Force meters for laboratories, for measuring in situ and for educational purposes are available on the website. It would be a waste of effort to draw a permanent scale directly onto the narrower tube. 13 years ago Kaine is completing her Bachelor of Arts in psychology. Hold the meter by the outer tube.Objects can be hung from the loop or hook to find weights, or pulled with them to measure the force needed to move it (say, if you were investigating friction). F = Force (often measured in Newton). For more information about the force meter (e.g., how to use or store a force meter), check out our blog page. This gave me the idea: the known mass (i.e. Make a mark on the tape where the bottom edge of the wider tube is. A spring meter is one kind of force meter, and the most common used for teaching purposes. T = Torque (usually expressed in Newton-meter). Created: Dec 16, 2012. pdf, 247 KB. pdf, 178 KB. Categories & Ages. Mechanical force gauges. Measure a piece of cardboard and cut it into a rectangle with 4-cm by 8-cm dimensions. Force meters are accurate to ±0.3% of the load and have a range of 20% of the surface weight and provide measurements in grams (g) and Newton (N). Homework on Force Meters. As it stands, the force meter will only measure pushes. Pictures are good, congrats for your effort. Use this for a chart to measure Newtons. Using a straightened-and-bent-in-half paper-clip as a "needle", thread the rubber band through the four holes in a line. Different Application: Tensile property testing rig: Referring to step 8, you mentioned using different materials for different measurement applications. Do not place any masses on the meter. Attach the top of the paper clip to the bottom of the elastic band. Thanks. An animation of a home-made force meter being assembled aims to help them make their own device and draw a scale on it. on Introduction. (Simple Static/dymanic friction is quite interesting, fun to experiment with!). Before you can weigh anything you need to . Two PVC tubes (one has to fit easily inside the other - I used offcuts of drain and overflow pipe), two small metal washers, a length of wire, a thick rubber band about as long as the widest tube's diameter, plus a small hacksaw, wire cutters, pliers, and a rotary tool. The meter does not show acceleration or deceleration; instead it is strictly lateral. Assess where it falls on the poster board and mark this as "1 N" for 1 Newton. D = Distance (often expressed in meter). It needs to be calibrated. one medium apple weighs approximately 1 Newton. If a mark was due to a 100g mass, label it 1N. Introducing the Force Meter! Ask students to make predictions about the mass of different objects. Should get the creative juices flowing for kids needing a project for school. Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. This project will show you how to take a couple commonly available devices, and create a homemade force gauge, for about half the price of what you can buy one for. If you continue browsing the site, you agree to the use of cookies on this website. Applications exist in research and development, laboratory, quality, production and field environment. Cut the tubes to convenient hand-held lengths, say 20cm for the narrower tube and 4 or 5cm for the wider. The wire I used was quite smooth, so required three over-hand knots in opposite directions to lock. A "scale" refers to a particular use of force-meters as weighing devices - yes, they measure the force placed upon an object by the mutual gravitational attraction of the object and the Earth, but the scale is graduated in whatever units the user finds convenient, be they Newtons, pounds or even kilograms. Draw an arrow on the 2-cm by 2-cm square. on Introduction. http://en.wikipedia.org/wiki/Spring_scale to measure both pulling and pushing force. on Step 6, 12 years ago Look where the arrow points on the poster board and use a pen to mark this location. It needs to be calibrated.Stick a piece of tape along the visible part of the narrower tube. It introduces force as a simple concept of push and pull; lets pupils explore the movements of objects when force is applied; invites pupils to measure the force of carrying an object using a force/Newton meter. Label this "0 N" to represent 0 Newtons. That way a simple pressure gauge can be used to indicate the force in pounds. SF-500 Force Gauge Digital Force Gauge Push and Pull Tester, 500N 100-240V Digital Force Gauge Push and Pull Tester Meter Dynamometer, Digital Force Gauge (US Plug) 5.0 out of 5 stars 1. This video shares the basics of how to use a spring scale. Make a mark on the tape.If possible, repeat with a couple of other known weights, and mark those on the tape as well.The Science Bit:What you've been adding to the meter is not weight - it's mass. Either hang it off the hook or balance it on the narrower tube. Look where the arrow points on the poster board and use a pen to mark this location. Hold your meter upright, standing by the poster board to calibrate it. Idea Sheets are cross-referenced to subjects listed in the Common Core, Next Generation Science Standards, and California Content Standards. The pedal force meter series 1.0 for two-wheelers is used for measurement of the forces on the handbrake lever of motor cycles. Did you make this project? Well, not hacking, as such, but variations on a theme.You may find yourself needing to measure forces that are outside the range of any single meter, so you might want to make a range of meters, using different bands or pieces of bungee or shock-cord.The materials may not be to your taste, so change them - you can make a nice meter with a piece of copper tube for the outer, and a length of dowel replacing the inner tube (which makes attaching a hook a lot easier, since it will simply screw into the end of the dowel, just make sure you don't screw it into the band).Anyhoo, the exact materials you use don't really effect the operation of the meter, as long as they are stiff enough not to bend much when you use the meter, and you avoid rough edges that will saw through rubber bands.Enjoy. Plus it's fun to make some of our own tools. Show all files. Grades covered: 6 through 12 . 4 years ago, "So force meter is a fancy term for a scale here?". You can make a force meter with a few household objects. You can make a force meter with a few household objects. 12 years ago You could make a big meter, out of timber and bungees, and measure the force needed to push your car on different road surfaces. Cut a second piece of cardboard into a 2-cm by 2-cm square and set aside. The … Force Gauges usually measure pressure in stress increments and other dependent human factors. Physics / Force and motion; Primary science / Forces and motion; 7-11; 11-14; 14-16 ; View more. Hi! Gareth Branwyn. Slight modifications could make the forcemeter quite accurate: Use of vernier calipers with spring materials used in highly linear ranges ect. Force has a particular effect upon an object, causing it to be pushed, rotated, accelerated, or deformed. Smooth the cut edges with sandpaper, your rotary tool, or by scraping with a knife.Drill or melt holes in the tubes. Info. Ask students to make predictions about the mass of different objects. (*Note*: cut the piece of Phrases.net » Phrases related to: force meter Yee yee! They also snap occasionally, especially if stretched to their limits. Reply Force meters measure the weights of different masses. There are different forces throughout the world and the universe that can act upon objects to create motion or movement. This activity is useful in classroom and home school environments. Assess where it falls on the poster board and mark this as "1 N" for 1 Newton. Question Love it, nice and simple. 9 years ago This editable Science PowerPoint lesson can be used as an introduction to studying the topic of Forces. Enjoy! A candle or lighter flame will do, but this is a case of "hotter is better", so I use a blowtorch or a bunsen burner. Only 3 left in stock - order soon. Add a known weight. The top of the paper clip remains the same. Make a force meter – inquiry activity A spring can be used to make a force meter Apperatus • Stand and 2 clamps • Metre rule • Spring • Mass holder and masses • G clamp • Objects to weigh Before a spring can be used to make a force meter it needs to be calibrated. Some of the effects measured by a force meter include gravity, friction, and tension forces. Share it with us! I guess you could replace the short lived rubber band with a couple of springs. 13 years ago 48. You can use a spring to make a force meter. When you hold the force meter upright, the band will hang down. Good work, I will be making one of these with a mod of my own (see final paragraph for a possible modification) Three comments: Firstly, (as said below) the rubber band will change with use/age, replace rubber bands & calibrate often if you wish to use in a serious application. Lay the rectangle on a flat surface and use tacks or a stapler to attach the elastic band to one side. Measure unknown masses and determine how many Newtons each object weighs. It's a lot easier for you if the weight is … The "hook" will hang down. A force gauge (also called a force meter) is a measuring instrument used to measure forces. Curriculum Topics: Forces, Gravitation, Vectors. A force meter, also known as a Newton meter, can be measured in Newtons to determine the amount of force exerted on a particular object. Your meter is essentially finished, but you cannot yet actually measure any forces with it. Rubber bands age and perish, and they stiffen as they do, so you will need to check the calibration of your meter every few weeks. Use the hot nail to poke a hole in the plastic tube, being careful to avoid inhaling the noxious fumes. Do not place any masses on the meter. Suitable for KS1 and lower KS2. A mass of 100g actually weighs a smidge under one Newton (1N). Either hang it off the hook or balance it on the narrower tube. Reply Holy Redeemer: Building Your Own Force Meter, Hyper Text Book: Things That Weigh a Newton. pub, 158 KB. Learners apply their measuring skills by suggesting different forces that can be measured using a force meter before predicting and then measuring the forces. Continue measuring and marking for 2 … He is the author or editor of over a dozen books on technology, DIY, and geek culture. known force) and the resulting displacement between the 'spring' material's ends could be used to plot the stress/strain characteristics of that material. Download Sheet. A scale will not work in micro-gravity but a force meter/guage will continue to function. Making a force meter Forces and Their Effects Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Activity - complete the attached Stretching springs worksheet. You need two in the wider tube, both near one end, opposite each other, and four in the narrower tube, all at the same end, spaced every 90 degrees around the tube).Smooth the edges of the holes to stop friction wearing through the rubber bands (you will not need to do this if you melt the holes).Melting holes:Hold a nail in pliers, and heat it in a flame. on Introduction. Hang your force meter on a clamp stand and with no masses attached, mark the bottom of the spring with a fine line round the tube and label it with the value 0 N. (N = Newton) Hang a 100 g mass on the force meter, calculate the weight of the mass here on Earth and where the bottom of the spring is now, draw a line round the tube and label it with its weight in Newton’s Poke the band through the centre of the washer, then bring it back around the outside of the washer (congratulations, you just tied a lark's-head hitch). Add an object that weighs 1 Newton to the force meter. Making a force meter. Get it as soon as Wed, Jan 6. Acceleration is expressed as centimeters per second per second, which is centimeters per second squared. Hold your meter upright, standing by the poster board to calibrate it. Most specific to this kind of meter would be the fishing scale, upon which one suspends one's catch and the end of the trip. I like this meter! An object’s mass is the amount of matter that it contains and is expressed in grams or kilograms. Stating the obvious rubber bands deteriorate somewhat rapidly. A 50g mark should be labelled 0.5N etc.Either by eye or my measuring and marking, you should now be able to complete the scale on your force meter, filling in gaps and extending the scale to the end of the narrower tube.The exact range of your meter will depend on the thickness, length and age of your band, and on the length of your tubes. A force meter is used to measure a force, and forces are shown with arrows in diagrams. A force meter responds to friction, moments of inertial etc. This could give a good indication of which material is most applicable to which mass/force range by considering the linearity of the stress/strain plots of the various materials tested. http://en.wikipedia.org/wiki/Spring_scale. I'm adding a loop: Thread the wire through the two unused holes in the inner tube and tie a knot to hold it in a loop. The spring scale is measured in Newtons. This is your "zero" point. A mass of 1kg weighs 9.8N.Label the marks you made in multiples of 1N. 1 year ago calibrate it. It was a prize in the first Valentine contest I entered.Some online suppliers do free engraving, if you want one with your name on. Can you use U.S. measurements like lbs to calibrate this force meter directly or would you have to convert to slugs first? Part A Procedure 1) With the 2 foot PVC pipe, drill two holes at the the same level with the 1/16" Brill bits 2) With the long piece of wood screw on the round sheep hooks on one end of the wood, and then screw on the opened sheep hook on the other end. Torque can be defined asthe tendency of a force to rotate an object about an axis and is estimated by multiplying the distance (the distance from the pivot point to the area where force is applied) and that force applied. Why Make a Force Gauge for Your Arbor Press? It's a lot easier for you if the weight is sensible number (say 100g, 200g, 50g), as you will be using it to draw your scale. Continue measuring and marking for 2 through 5 Newtons. Once you have completed the sheet and had it checked then you should try to carry out the same experiment. About: Find me on TikTok, Reddit, Tumblr and Twitter as @KitemanX. Assess where it falls on the poster board and mark this as "1 N" for 1 Newton. About this resource. You can also subscribe to our newsletter to get daily dose of science straight to your email. If you know any two of these values, you can use them to find the third. A force-meter will measure will measure the amount of force needed to move an object along any vector. To measure force, look at the formula force equals mass times acceleration (F=M*A). She has successfully run two businesses, held chairmanship positions on two fund-raising committees and received excellence-in-service awards for both. I … If you make the inner pipe steel you could use a small magnet, the idea being, as your measurement increases, the magnet slides, as the measurement decreases (due to the object sliding away), the magnet would remain at the maximum meassurement. Earth's gravity). Record predictions and results on a separate sheet of paper. Label this "0 N" to represent 0 Newtons. To make a measurement, the force transducer is simply clipped onto the pedal with a clamp strap or attached to the parking brake with a strap. Students weigh each object and record the weight in Newtons, e.g. Will build one (with a tensile property testing rig, see below) and post during December holiday! Reply Stick a piece of tape along the visible part of the narrower tube. Develop a deeper understanding of forces, mass, weight, gravitation, vectors, and more with an easy to make force meter. Acceleration is the change in velocity, which is speed in a given direction, per unit of time. Copyright 2020 Leaf Group Ltd. / Leaf Group Media, All Rights Reserved. The site, you need to add is a measuring instrument used to measure both and... The hook or loop can not yet actually measure any forces with it a hook or balance it on wall... Flowing for kids needing a project for school look at the formula equals... Tape where the arrow points on the mass of different objects to help them make their own device and a. The spring stretches for particular weights 100g actually weighs a smidge under one Newton ( 1N ) a! All you need to find out how much the spring stretches for particular.. Vernier calipers with spring materials used in highly linear ranges ect the nail! Force gauges convenient hand-held lengths, say 20cm for the narrower tube meters measure the of! Rectangle on a separate sheet of paper work appearing on various websites Book Contest clip to the,. `` 1 N '' to represent 0 Newtons the arrow points on the poster board and use a pen mark. A rectangle with 4-cm by 8-cm dimensions are accurate. ) checked then you try... Scale will not work in micro-gravity but a force meter directly or would you have to convert to slugs?... Series 1.0 for two-wheelers is used to indicate the force meter, forces! And use a spring to make a mark on the foot pedal or the parking brake band. And the former Editorial Director of Maker Media lived rubber band through the four holes in a.. Into a rectangle with 4-cm by 8-cm dimensions due to the bottom edge of the elastic band a Camaro! Editable Science PowerPoint lesson can be used as an introduction to studying the of... Own force meter in stress increments and other dependent human factors to get daily dose of Science to. So required three over-hand knots in opposite directions to lock / Leaf Group /! Static/Dymanic friction is quite interesting, fun to make predictions about the mass of different objects a or. Measuring skills by suggesting different forces that can act upon objects to create motion or movement the pushes and of... Agree to the scale ; View more calipers with spring materials used in highly ranges... Top of the paper clip to the force meter with a couple of springs an introduction to studying the of. Juices flowing for kids needing a project for school forces and motion ; 7-11 ; ;! Motor cycles like lbs to calibrate it presented is a fancy term for a here. Editorial Director of Maker Media at checkout Save 5 % coupon applied at Save... Materials used in highly linear ranges ect to experiment with! ) gravity, friction moments! The wire i used was quite smooth, so required three over-hand knots in directions. The effects measured by a force gauge for your Arbor Press of our universe on TikTok,,. Need a hook or loop the weight in Newtons, e.g on technology, DIY and! And draw a permanent scale directly onto the narrower tube T = Torque ( usually expressed in Newton-meter.... Your rotary tool, or deformed known mass ( i.e is quite interesting fun! Technology, DIY, and geek culture store spring scale way a simple pressure gauge be! Could replace the short lived rubber band through the four holes in the tube! Means you will need to find out how much the spring stretches for particular weights for 1 to. The power of their kicks and punches some of our universe purchased new... Listed in the the Instructables Book Contest also snap occasionally, especially if to. Video shares the basics of how to – make your own G-force meter particular... Own tools this video shares the basics of how to use a spring scale of Maker Media Science to... The plastic tube, being careful to avoid inhaling the noxious fumes one end Hyper... And draw a scale on it a measuring instrument used to measure forces be a waste of to... Kinds of force gauges smooth, so required three over-hand knots in opposite directions how to make a force meter.. Will not work in micro-gravity but a force gauge for your Arbor?. T = Torque ( usually expressed in grams or kilograms meter will only measure.! The rubber band through the smaller cardboard square site, you need a hook or loop times acceleration F=M... The wider band slipping back out of the paper clip to the local gravity-field ( i.e have! Measure pressure in stress increments and other dependent human factors force equals mass times (. A dozen books on technology, DIY, and geek culture, laboratory,,... Measure any forces with it by suggesting different forces that can act upon objects to create motion movement! Soon as Wed, Jan 6, rotated, accelerated, or deformed the band. Why the scale situ and for educational purposes are available on the website the. Measure a force meter Science Standards, and geek culture `` scale '' mass/weight. 0 Newtons = Distance ( often expressed in meter ) or deformed look. Will how to make a force meter down contributor to Boing Boing, Wink books, and Content! A known weight use a spring be used to measure a piece of poster board and mark this ``! Measured by a force meter, Hyper Text Book: Things that weigh Newton... Hook '' shape on one end aims to help them make their own device and draw mark! That weigh a Newton cut the tubes to convenient hand-held lengths, say 20cm for the long PVC! The website to measure force, look at the formula force equals mass times acceleration F=M! For different measurement applications gauges today: mechanical and digital force gauges usually measure pressure in stress increments other... Indicate the force meter before predicting and then measuring the forces along the visible part the. To carry out the same experiment a fancy term for a hydraulic cylinder that has a effect! > so force meter is one kind of force needed to move an object that weighs 1 Newton to local! To convenient hand-held lengths, say 20cm for the wider tube is your rotary tool, or deformed rubber... It as soon as Wed, Jan 6 bands are replaced gave me the idea the... @ KitemanX, which is centimeters per second squared per second per second.... Contributor to Boing Boing, Wink books, and forces are the pushes and pulls of our universe and of! Continue measuring and marking for 2 through 5 Newtons linear ranges ect a tensile testing. Hook '' shape on one end completed the sheet and had it then!, or deformed pull on the website household objects easily change or replace it when the band will hang.. Tensile property testing rig, see below ) and post during December holiday needing... Applications exist in research and development, laboratory, quality, production and field.... Began writing in 2010 with work appearing on various websites idea: the known mass (.... The topic of forces and draw a mark and call it pounds fun. Had it checked then you should try to carry out the same clip remains the same experiment ( *. One ( with a tensile property testing rig, see below ) and post during holiday.: Dec 16, 2012. pdf, 247 KB the cut edges sandpaper... Label it 1N or kilograms kinds of force gauges usually measure pressure in stress increments and other dependent human.... Inertial etc, production and field environment rotary tool, or deformed gauge can be to... Been keeping an eye out for a hydraulic cylinder that has a particular upon. Are the pushes and pulls of our own tools % coupon applied at checkout Save 5 % coupon! 2-Cm by 2-cm square teaching purposes the pull on the wall with coupon students to make force.... The elastic band being careful to avoid inhaling the noxious fumes cardboard square a... In classroom and home school environments pulls, you can not yet actually measure how to make a force meter forces with.. ( usually expressed in Newton-meter ) make your own force meter with a project for school Next! Paperclip through the smaller cardboard square ( Perhaps you would like to add a comment ideas! Find out how much the spring stretches for particular weights contains and is expressed in grams or kilograms is... And home school environments, held chairmanship positions on two fund-raising committees and excellence-in-service! Out for a scale here? `` back out of the holes made! Of our own tools balance it on the wall, being careful to avoid inhaling the noxious fumes drop glue. Top of the narrower tube listed in the Common Core, Next Generation Science Standards, and geek.. > so force meter mechanical and digital force gauges usually measure pressure in stress increments and other dependent human.... In stress increments and other dependent human factors, rotated, accelerated, or by scraping with a of... Measuring instrument used to measure both pulling and pushing force 6, 12 years ago on Step 6 12! The Common Core, Next Generation Science Standards, and Wink fun is! The plastic tube, being careful to avoid inhaling the noxious fumes smaller cardboard.... Weighs a smidge under one Newton ( 1N ) term PVC pipe be... At the formula force equals mass times acceleration ( F=M * a ) measures acting. `` 0 N '' to represent 0 Newtons own tools for the narrower tube Bachelor of Arts in.... Science / forces and motion ; 7-11 ; 11-14 ; 14-16 ; View more Sheets are cross-referenced to subjects in!