A wee alarm bell is ringing re your figures in calculating the G forces applicable during the spin cycle. Mass doesn’t come into the equation as we are calculating the force applied to any mass present in the drum.
I dimly recall from working in hospital laboratories in a previous life that the formula for calculating G was <0.0000112 N2 r> where N was the rpm(squared) and r was the radius in metres.
From the quote you posted: “too much blood being forced into your brain makes you “red out,” and that’s no good either.”
You can withstand more than 30m/s of acceleration towards your feet and still be able to see, just some blood will drain to your legs and you might get a bit pale. More than 70 or 80 m/s, as the limit says, can knock you out or worse.
However, when you’re upside down and the 30 m/s acceleration is directed to your head, you can’t see. You ‘red out’. Too much blood in your head. Since we’ve evolved to walk upright, it’s no coincidence that our bodies are better at withstanding acceleration towards our feet, like gravity, than towards our heads.
Even in cheap flight sims they make you red out if you pull too many 'g’s in the wrong direction.
You are correct. However, if you look closely at the staff report, you’ll see that, in the final equation, the mass cancels out. From the Staff Report: “So the number of g’s is [symbol]w[/symbol][sup]2[/sup]r/g.” No mass.
Oh! Now I see that it was the language that was confusing me.
I imagined that they strapped me “upside down” into the roller coaster. What they must have meant was, "when the roller coaster car is travelling “upside down” on one of its loops, then you are limited to 3 g’s or whatever.
Fascinating. The figures check, and I would not have guessed that the G force in a washer was anywhere near that high. For one thing, I didn’t think they rotated that fast. I’d have guessed maybe 3 times a second, which would have led me to ballpark around 8 to 12 G’s, since it depends on the square of the angular velocity.
However, a little poking around confirms that 600 RPM is a pretty typical washing machine spin cycle, and that extraction force will be in
the 100 - 200 G range.
Even then it’s not quite right. In a normal loop, you go upside down, and yet the g forces are still toward your feet. You can withstand a loop that puts you under more than three times the acceleration of gravity.
That sentence, “If you are upside-down in a roller coaster…” is basically just inaccurate, which is causing the confusion. The easiest way to produce the negative g’s, if you wanted to make your riders “red out”, would be to have them go over a parabola from straight forward to downhill that is faster than the ballistic parabola that would give you zero g’s. Alternatively, you could invert your riders at the bottom of a hill, then they’d be getting the negative g’s. Essentially, you could take any roller coaster bit that produces acceleration in some direction, and make sure it’s to the rider’s head.
I have a sinking feeling that I haven’t helped at all. The point is somewhat moot, I doubt many rollercoasters put their riders under significant negative g’s. Putting them under zero g’s is more simple and interesting, and produces an effect like freefall or microgravity rather than one of standing on your head.
Things are much simpler in a car, where it’s impossible to put a rider under negative g’s as long as the car is on (or lands on) its wheels.
If you have 20 pounds of laundry times 118 g’s that would weigh the equivalent of 2360 pounds? Am I missing something? How would it be possible for a washer to hold that weight? Or your floor?
Ummmmm - why is this tomorrow’s staff repot, and why is it already linked to from www.fark.com? Isn’t tomorrow’s stuff, well, tomorrow’s stuff, and not today’s? I’m confused… Do the mailing list people get these articles that much in advance, or did I forget the date and this is really a classic?
Sorry for the hijack, but this is, I think, the thread in which I’ll likely get a decent answer
The weight on the floor doesn’t increase or decrease, unless the load is really off-balance.
The washer’s tub is usually round, and round is a good shape to withstand the pressure from the acceleration of the clothes.
If the tub is two feet deep and two feet wide (made up numbers, washers vary) then the surface area of the tub that would be covered by clothes when spinning would be pidh. pi is 3.14159, the diameter is 24 inches, and the height is 24 inches. That’s a total surface area of about 1800 square inches. 2360 pounds over 1800 square inches is about 1.3 pounds per square inch (psi), easily sustainable by metal or plastic.
For reference, regular kitchen aluminum foil can withstand about 15 psi.
Most washer tubs are made of stainless steel, plastic, or painted steel that is significantly stronger than aluminum foil, so we can see that the strength is more for rigidity and durability than any worry about the clothes exploding through the washer.
Mnemosyne: << Isn’t tomorrow’s stuff, well, tomorrow’s stuff, and not today’s? >>
People who subscribe to THE STRAIGHT DOPE get an email on Friday that provides a link to that days’ column by Cecil, as well as to the Monday classic column and the Tuesday Staff Report of the next week…hence, they get an advance peek.
To subscribe, go to the STRAIGHT DOPE homepage and scroll down a wee bit, and you’ll see a link that will subscribe you. Then you, too, can discuss events before they happen!
Do you use separate spin-driers, do you use mostly clothes lines, do you accept your electric driers to take 3 hours, are your gas driers that much more powerful, is your energy cheaper in general, or why don’t you need to bother with a more efficient spin cycle (sounding like a jet-engine, but creating 500 g)?
Yeah, yeah, lets talk up the technical stuff, but what about those poor bastards in the parallel universe that are getting stuck with all of the odd matched socks?
This one time, in washing machine school, the teacher was telling a story about this guy that extracted fish oil from dead fish by putting them in a washing machine fixed to run a heated spin cycle! Talk about a sticky situation! (and smelly too).
-Sandwriter
p.s. I had to say that the fish were dead to kill all the, “…I hope the fish were dead…” posts.
Washing machine school? What was the subject, repair or use? One might note that since missing socks are [allegedly] spun into some nearby parallel universe, consider that the odd sock might possibly of have smelled of well … smelt or whatever fish is was that were [allegedly] spin desicated.
I’m having a bit of trouble understanding the formula. I don’t see how pi fits into it unless we’re talking about tangential velocity instead of angular velocity. Karen, could you clarify, please.
I found a formula on the web (courtesy of Google) that seemed to avoid the radian issue by using tangential velocity instead of angular velocity. It gave the same answer but didn’t fake me out. I hope I remember all this the next time it comes up.
I’ve reached the point in life where each time I learn something new I have to forget something old. Problem is, I don’t get to choose what I forget.
Do the mailing list people get these articles that much in advance, or did I forget the date and this is really a classic?
