Structures and Mechanics with fischertechnik Levers and Scales – Level 2

1. Structures and Mechanics with fischertechnik Levers and Scales – Level 2

2. What You’ll Learn… • History of scales and measuring weight • How the principles of levers apply to balance scales • The mechanical principles of balance scales • The mechanical principles of sliding weight scales Stuff You’ll Need… • Fischertechnik Profi Mechanic + Static Set • Mechanic + Static Activity Booklet • Mechanic + Static Assembly Instruction • Digital camera

3. ePortfolio Suggestions… • Before you begin the activities in this Learning Launcher, write down anything you may already know about scales and how they work. • List three interesting things you learned from the What You Should Know… section. • Keep a glossary of new words you learn. Pay particular attention to the bold, italicized words you find. • Take pictures of your fischertechnik models and label each of the parts. • Describe the process you used to calibrate your sliding weight scale. • Answer each of the questions in the Activity Booklet. Record your observations in your Project Planner. • Create a narrated video demonstrating how your scales work.

4. What You Should Know… Before beginning the activities in this Learning Launcher • You should already be familiar with the fischertechnik construction system. • You should be familiar with the different types of simple machines and understand the basic principles of each. • You should understand the principles of levers and be able to calculate mechanical advantage. If you are not familiar with any of these concepts, you should review the What You Should Know… section of the Level 1 Machines and Gears Learning Launcher.

5. What You ShouldKnow… Getting to know fischertechnik… fischertechnik is a precision modeling system designed and produced in Germany. Like many modeling systems, fischertechnik is a great way to model structures and machines on a small scale. Unlike many modeling systems, fischertechnik is the choice of scientists and engineers for sophisticated modeling simulations and experiments. fischertechnik can be used to model large structures and simulate complex machines. With its sensors and computer programming capabilities, fischertechnik is even a sophisticated robotics system. If you have not worked with fischertechnik before, take the next 15 minutes and explore your fischertechnik Mechanic + Static collection. If you have worked with fischertechnik before, proceed to the next slide.

6. What You Should Know… The History of Weights and Measures… People have always needed to trade with each other. The buying and selling of goods between people is called commerce. In order for commerce to function in a society, both buyers and sellers need to feel like they are being treated fairly. Much early commerce revolved around goods that were traded based on weight, such as agricultural produce. So for thousands of years, we have had needed to compare the weight of objects against a standard so everyone could agree that they were getting a fair deal. Scales were developed for this task. In fact, this concept of measuring weightto determine fairness is so central to society that it became our very symbol of justice! Lady Justice

7. What You Should Know… The History of Weights and Measures… One of the earliest machines used to measure weight is the balance scale, also called a beam and scales. Balance scales are a type of simple machine called class 1 levers and operate like see-saws. They consist of a beam suspended by a fulcrum (either from above or below) positioned at the mid-point. Platforms or trays are positioned at each end of the beam to hold the objects being weighed. If an object of known weight is placed in one platform, the beam will balance when an object (or objects) of equal weight are placed in the other. Thus, you can use a known weight, a standard,to establish the weight of an unknown. Balance scales were used as early as the Babylonian Empire over 4000 years ago. The first known units of weight were stones. During the time of the Roman empire, grains of wheat, which were very uniform and accurate, were used as the standard of weight. Farmers could establish the value of their crop by comparing to these standards. Ancient Roman Beam Scale

8. What You Should Know… The History of Weights and Measures… The balance scale worked well as long as your goal was to measure objects of equal weight. But there was often the need to measure objects of unequal weight. This need led to the development of the sliding weight scale. If you’ve ever tried to see-saw with your little brother or sister, you may have had to inch up towards the middle to find a point where you both balanced. The sliding weight scale works on exactly the same principle. By using a moveable known weight and calibrating the beam, we can measure objects that weigh more or less than the standard weight. Ancient Roman Sliding Weight Scale

9. What You Should Know… Levers and Scales The sliding weight scale is just another class 1 lever with force applied by gravity acting on the mass of an object. Let’s look at how it works. The tray with the object we want to weigh is on the left. The beam is suspended (either from above or below) by a fulcrum at a fixed point. In this example, the center of the tray with the unknown object is 1 ft. from the fulcrum. If the scale balances when the sliding weight is the same distance from the fulcrum we know that the unknown object weighs 5 lbs. (equal to the sliding weight). This is essentially the same as the balance scale. To be perfectly precise, we’d need to take the weight of the beaminto account too when calibrating our scale. But, to simplify these examples, we’ll just ignore it for now. Unknown Object Sliding Weight ? lbs. 5 lbs. Distance 1 ft. Distance 1 ft.

10. What You Should Know… Levers and Scales If the scale balanced when the sliding weight was 6 inches from the fulcrum we would know that the unknown object weighed 2 ½ lbs. Since the distance from the fulcrum to the sliding weight is half that of the unknown object, it applies one-half the mechanical force. This type of mechanical force is called torque. Unknown Object Sliding Weight ? lbs. 5 lbs. Distance 1 ft. Distance 6 in. With what you now know about this kind of machine, can you determine how much the unknown object weighs if the scale balanced when the sliding scale was 2 ft. from the fulcrum? How about 3 ft?

11. Do It! Building the Beam and Scales… Now that you know the basic principles of scales, let’s build some models to learn more! Find the Activity Booklet in your Mechanic + Static kit. Turn to page 33 and build the Beam and Scales as shown. You can find assembly instructions on page 44 of the Assembly Instruction book. Beam and Scales Be sure to answer the questions in the Activity Guide and record your answers in your Project Planner! Assembly Instruction Activity Booklet

12. Do It! Building the Beam and Scales… Did you notice that your beam and scales is constructed with two beams? Think about the function of this double beam construction and why it might be useful for this kind of scale. Take another look at the early Roman Empire balance scale in the What You Should Know… section. How does that design address this same design consideration? Beam and Scales

13. Do It! The Sliding Weight Scale… Next, build the Sliding Weight Scale on page 34 of the Activity Booklet. Assembly instructions can be found on page 70 of the Assembly Instruction book. Ask your Facilitator for a set of standard weights and use these to calibrate the arm of your scale. Sliding Weight Scale Assembly Instruction Activity Booklet

14. Spring scales are another common machine used to measure weight (typical bathroom scales are spring scales). Go online to learn how they work. The study of weights and measures is called metrology. Go online to learn more about this area of science and people who work in this field. Try building some of the other structures in the Mechanic + Static Assembly Instruction book. Or design one of your own. Try building one of the structural devices in the Mechanic + Static Assembly Instruction book. Go online and search for “fischertechnik projects”. Check out some of the amazing things people have built using this sophisticated modeling system. Extend Yourself…