Grain - the word, the term, the application - Explanations Wanted.

[1KPerDay]

Didn't see anyone mention it, but black powder loads are also measured in grains, but it's by volume, not weight. Just to add some more confusion.

 

[akodo]

In science both the Pound, and the Kilogram are units of mass(2.24lbs=1kg). To get Force(F=ma) you must multiply the unit of mass times a unit of accelertion (Newtons ("N") are the prefered unit)(1N = 1kg * -9.8m/s^2)(-9.8m/s^2 is the accerelation due to gravity on earth)

I am going to take the opposite. Kilograms are mass, Pounds are not. Stones, and grains, however, are also mass. Pound is a measure of X mass being pulled on with earths' gravity. That's why you are able to have X pounds of force, from say, a baseball hitting a window or whatever. It's why you will weigh less pounds on the moon than you do on the earth, but your kilogram value for your mass will remain the same. We of course use them as if they are interchangable but of course they are not. Scales and such are simply calibrated to read off the correct one when used at earth's gravity. At least scientifically that is the case. Of course the US gov has declared that the lb is the offical measure of mass. Really, this is like fluid ounces. Of course, ounce is a measure of mass, and a fluid oz is defined as the volume of space needed for one oz weight of water. The same thing happened with pound when the US gov stuck it's nose in, they really ignored the true scientific definition of lb for convenience, because everything was already in lbs, and they didn't want to have to start measuring stuff in another unit.

You may as "So if a grain is such an ancient measurement that it is based on an actual grain from a field of crops, how do you know if the people back then who first started using it were measuring force or mass? They probably had no concept of either term!"

Well, it goes back to the most primitive ways of weighing and measuring stuff, the balance (the scales that blind lady justice holds)

Simply put, you have a bar on a pivot, you put known weight A (a kernel of barley, or ) and you put enough stuff on the other end until the bar is level.

Gravity pulls down evenly on both sides, so for the simple balance, gravity is nicely canceled out of the equation. If your gold wedding ring balances out against 500 grains of barley here on earth, you can take that same ring and a buhch of barley to the moon, and it will balance out there too...because gravity is pulling on both sides and canceling itself out of the equation.

Of course, rather than use barley corns, you can have a nice little set of lead blocks chosen to balance out at exactly 10, 100, 1000, etc etc barley corns. To be even fancier, you can have the pivot point somewhere other than the middle, and as long as your set of lead blocks is calibrated to be used on this uneven bar balance, no problem. This is basically how the 'scales' (hey it is really a balance) like you see in a doctor's office works.

Now, another method of measuring was developed some time later, that was the scale, which is what you have in your bathroom at home. It is basically a spring. The harder you push on it the more the spring compresses. When you stand on it, or place something on it, you are measuring how hard gravity is pulling down, by seeing how far the spring is compressed, you are measuring force. This is also why you could set your bathroom scale on the kitchen table, sit in a chair, place your hand on the scale, and push down as hard as you can, you are able to measure how much force you are pushing down with. Scales are simply calibrated to work under earth's gravity. Take for example an early scale. It was quite simple to take a barley grain and place it on there, then measure how far the spring moved, draw a line and put 1 grain there, then put on 2, then 3 etc etc. So you place your same gold ring on the scale, and the spring compresses to the same degree as it did with 200 barley corns, that compression of the spring is a measure of force, but it has been converted into a measure of mass. The truth of the matter shows up when you bring a scale to, lets say, the moon. Because the moon has much less gravity, your gold ring woudn't push the spring down as far as it did on earth, probably hanging out around the 80 barley corn line. Of course, the traditional balance, with your ring on one side, it woudl still take 500 grains on the other side to balance it out.

 

[carebear]

What a great explanation.

Thank you.

 

[brickeyee]

There is an entire weight system now rarely used.
The Apothacary system.
Based on the grain, it includes scruples (20 grains), the dram (3 scruples), the ounce (8 drams) and the pound (12 ounces). The base grain unit is the same fer the troy, apothecary, and avoirdupois systems. The pounds are 5760 grains for troy & apothecary, and 7000 grains for avoirdupois. The change occurs at teh ounce level (16 vs. 12).

Drams still show up in shotgun loadings and are tied back to black powder weight of the powder used.
The modern 'dram equivalent' produces the same velocity as the stated BP weight using smokeless powder.

 

[moewadle]

One clarification about what Juna said

above. He said that a pound is a unit of weight and kilogram is a unit of mass. That is not true. A kilogram is simply 2.2 pounds. Mass is "resistance to movement" and is the same everywhere in the universe for any given object. Weight is different on different heavenly bodies. A one-pound clay material brick will have the same mass on Earth and on the Moon and on Mars. However, it will not weigh one pound on all three of those heavenly bodies. As long as you stay on Earth you pretty much can use mass and weight interchangably but once you get into moving out of our gravitational system weight changes for any given object while the mass stays the same.