The metric system also uses water to define mass: 1 litre of waterweighshas a mass of 1kg.
Unfortunately, this has not been true for over a century. When the kg was defined as the mass of the International Prototype Kilogram, it stopped being possible for anyone to reproduce the kg in their backyard.
SI doesn't facilitate anything versus Imperial units. It's just an arbitrary re-scaling of quantities.
The metric system also uses water to define mass: 1 litre of waterweighshas a mass of 1kg.
Unfortunately, this has not been true for over a century. When the kg was defined as the mass of the International Prototype Kilogram, it stopped being possible for anyone to reproduce the kg in their backyard.
Well, it started out that way - and it's still close (1.000028 litres)
SI doesn't facilitate anything versus Imperial units. It's just an arbitrary re-scaling of quantities.
Actually, it does. It puts similarly dimensioned quantities on a common footing and allows calculations to be done without awkward conversion factors appearing everywhere. The most troubling for new students is the appearance of gc in many formulas to convert between mass and force (and woe betide you if you accidentally multiply by gc when you need to divide).
Beyond that, consider calculating the compressor horsepower to compress 100 cfm of air from 15 psi to 100 psi. Suddenly you have got hp, ft, lbf and minutes all mixed up in one formula. There is going to be a "magic number" in that formula that converts all the incompatible units. You'd better have a good memory for conversion factors. Every formula will have a different magic number in it.
The metric system also uses water to define mass: 1 litre of waterweighshas a mass of 1kg.
Unfortunately, this has not been true for over a century. When the kg was defined as the mass of the International Prototype Kilogram, it stopped being possible for anyone to reproduce the kg in their backyard.
The international prototype was achieved by equating the mass of 1 liter of distilled water at a bit lower than 4 degrees C when water is at its highest density at one Atmosphere of pressure, probably at sea level.
That's still true. However there are efforts to change that using Planck's constant as well as the Avogadro initiative.
Edit: but if you make a container that holds 1dm^3 of distilled water and chill it to 3.984 C you'll get a kilo if you are by the beach
I'm afraid you are going to lose that one. It is widely accepted in the English speaking world that "America" is short for "United States of America" when the context is a country (and by the way, I am not American).
And thence my gripe about measuring torque in the units of gm-cm. You can't multiply gm-cm by rotation rate and get units of power. You have to remember one of those "magic numbers", and remember that it is necessary.
Robertson screws are far superior to Philips.
https://en.wikipedia.org/wiki/List_of_screw_drives#Robertson
No slippage and the screw stays firmly on the screwdriver at almost any angle.
Unfortunately, they are virtually unknown outside Canada.
QuoteRobertson screws are far superior to Philips.
https://en.wikipedia.org/wiki/List_of_screw_drives#Robertson
No slippage and the screw stays firmly on the screwdriver at almost any angle.
Unfortunately, they are virtually unknown outside Canada.The Robertson screw has a different set of compromises, is all. Screwhead must be fairly deep. The bit gets seized/stuck in screw with significant torque (say you are removing a lot of high torque screws.. you may have to tap/wiggle each screw to get them off the bit, similar to a hex head). The angle between the driver and screw must be straight. And the screwhead impression must be in a particular set of sizes.
One of the greatest advantages of Phillips is that you can drive a Phillips head screw with the wrong Phillips head bit. They overlap to a large degree. With one or two Phillips head bits, you can do nearly anything. If you have the wrong size Robertson head, you are SOL. I don't see Roberson as doing anything that hex or torx doesn't accomplish better. (A Robertson "allen key", for instance, would need a room to make at least a 90 degree arc to be useful, compared to a hex head). Also with a phillips, you can also drive a screw at a slight angle between the screw and driver.
And it's known in the USA, just fine. I'm curious if it is actually the most common type of screw in Canada.
Robertson is common in home construction type stuff.
But Robertson is more or less found only in Canada. It is not common anywhere else.
There are No. 1, 2, 3 Robertson sizes... same as Philips.
For my woodworking, I have switched to Robertson (square-drive) screws. The self-holding feature is great.
I use them also for larger machine screws, but there is a much better availability of machine screws in Phillips head. Recently, I have concentrated on truss-head stainless Phillips screws for electronic assembly. McMaster Carr is an excellent source for machine screws in all shapes, sizes, and material.
In another thread, I mentioned "Reed and Prince" screws, which were used in classic -hp- gear. They look like Phillips drivers, but there is only one size driver for several head sizes, and the blades are subtly different. The only place I could find the drivers was the Sears Craftsman website (but not Sears stores), where they were available for about the same price as "normal" Craftsman screwdrivers. I haven't found them in hex-drive bits. If you are working on -hp- gear from 1960 to 1980, I recommend this driver.
And it's known in the USA, just fine. I'm curious if it is actually the most common type of screw in Canada.
You want to print all the labels to install in all battery powered equipment to swap the + and - ? And then convince the battery makers to do the same ?
Good luck
If I connect a 10 ohm resistor across a 1.5 V battery then a current of -0.15 A
flows from the negative terminal to the positive terminal.
If I connect a 10 ohm resistor across a 1.5 V battery then a current of -0.15 A
The maths might be OK - but I'm also considering the language. For example:Quoteflows from the negative terminal to the positive terminal.
The 'FROMs' and 'TOs' will need to be reversed, or the sentence structure will not match the concept.
Knowing how it all works out makes it easy to comprehend when looking back, but it's going to confuse the newcomers even more than they are now.
You realize I had my tongue in my cheek, right?