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# beam balance working principle

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From Wikipedia

Spring scale

The spring scale apparatus is simply a spring fixed at one end with a hook to attach an object at the other. It works by Hooke's Law, which states that the force needed to extend a spring is proportional to the distance that spring is extended from its rest position. Therefore the scale markings on the spring scale are equally spaced.

Spring scales can be calibrated for the accurate measurement of mass in the location in which they are used, but many spring scales are marked right on their face "Not Legal for Trade" or words of similar import, due to the approximate nature of the theory used to mark the scale. Also, the spring in the scale can permanently stretch with repeated use.

If two spring scales are hung one below the other in series, each of the scales will read the weight of the body hung on the lower scale. The scale on top would read slightly heavier due to being stretched by the weight of the lower scale.

Spring scales come in different sizes. Generally, small scales that measure newtons will have a less firm spring (one with a smaller spring constant) than larger ones that measure tens, hundreds or thousands of newtons.

## Uses

Spring scales can be used in physics and education as basic accelerometers, but its main uses are industrial, especially related to weighing heavy loads such as trucks, storage silos, and material carried on a conveyor belt. Spring scales are used when the high accuracy afforded by other types of scales can be sacrificed for simplicity, cheapness, and robustness.

## History

The first spring balance in Britain was made around 1770 by Richard Salter of West Bromwich. He and his nephews John & George founded the firm of George Salter & Co., still notable makers of scales and balances, who in 1838 patented the spring balance. They also applied the same spring balance principle to steam locomotive safety valves, replacing the earlier deadweight valves.

Question:My teacher told me that even if I went on the moon, my mass would stay the same. But if I calculated the mass of a rock on Earth with a triple beam balance, go to the moon, calculate it there with a triple beam balance, would the mass be the same? Doesn't a triple beam balance need the same amount of gravity in order to calculate the same mass?

Answers:Yes, the balance does need gravity to work. But it doesn't need the same gravity. It measures mass by Newton's 2nd law applied to rotational motion. Specifically, when you "balance" the scale you make the "sum of torques" equal to zero. And since the lengths of the beams and the masses of the weights are well known, you can infer the mass of the test object. You can work out the math and see that the acceleration due to gravity will cancel out of the equations. This means that any value for the acceleration other than zero is acceptable. But a zero acceleration means no gravity. So, if there is gravity, then the beam will work (independent of the acceleration due to gravity). So yes, your teacher is right. You might be confusing weight and mass. The mass will be same, but the weights are absolutely different.

Question:just sand it or would it not work good? do i have to put something over it, like the normal balance beams have that material on them, do i need that? if this would work, would would be a good way to make a balance beam?

Answers:im not a gymnast but I am a home improvement contractor. If your balance beam needs to be 12 ft long i would use a 6"x6"x12' post and rip it down to 4" (if thats the width you need it) otherwise the 6"x6" actually measures 5 1/2" you could sand it down and coat it with a polyurethane finish. but make sure you dont sand it after the poly cuz id imagine that you would want some kind of grip on it. Not covering it with a normal balance beam material might get kinda hard on your feet after a while though. so you might want to look into covering it with something.

Question:I have an old Pelouze metric precision scale (model R-47) that has left & right trays and weights in grains and grams. It used to work perfectly, but it's been sitting in a closet for a few years, and when I took it out to use it the scale seems "stuck". I adjusted the counterpoise nut and even the "sensitizer" disc under the beam, and I can get the scale to balance out at zero (where the 2 red lines in the center of the beam are even), but as soon as I gently tap either the left or right tray, the scale dips and never goes back to zero - it just stops and stays "stuck" and unbalanced. I gently cleaned it, oiled all the moving parts, and jiggled it around, but I can't fix it. It used to work perfectly, and it hasn't been jostled or bumped around. It's just been sitting in a closet for a few years. I even called the Pelouze Scale Company, but their records only go back 5 years and this scale it at least 25 years old. Does anybody know what more I can do to get working properly?

Answers:Cleaning is probably the solution. Depending on the type of materials used in the pivots they might be better off without oil (glass or agate for example) but if they are designed to be oiled the the old oil may have become gummy over the years and may need a solvent to remove the deposit. By the way, WD-40 is infamous for eventually becoming gummy, but it is a good solvent, so WD-40 followed by, perhaps, alcohol might do a good job, then if the bearings need oil, a light instrument oil. You might also check to see if anything has become bent and is rubbing anywhere, especially check the damper mechanism if it has one

Question:Whenever i go up to show off my tricks for gymnastics im like a earthquake but only on the balance beam. I work my ass off during practice to make sure i have everything i need to do and stick everything correctly but when i go up to compete i shake like no other and i fall and do really bad....HELP ME PLEASE!!!! I wanna stick just 1 routine down

Answers:I would suggest streching before the beam, and when on it, just take slow steady breaths. Dont think about who is looking at you, just focus on the beam itself. A good tactic is to ignore the people there. Dont look at them or make eye-contact, just look down at the beam and things should be fine. :) Usually, when I balance on things, I look down at my feet to make sure I have them placed correctly. XD