A Staff Report from the Straight Dope Science Advisory Board

How many G's does my laundry pull during the spin cycle?

August 13, 2002

Dear Straight Dope:

How many gees does my laundry pull when the washing machine goes into its spin-cycle?

I'd love to tell you how many g's your laundry pulls, Greg, but I'm a physicist, not a psychic, and you didn't give me any of the specifications of your washing machine. So I'm going to tell you how many g's MY laundry pulls. I'll tell you all the equations, though, and you can repeat the calculation for your own laundry.

The force my laundry experiences is equivalent to the centripetal force required to spin it in a circle, and from our elementary physics we know that centripetal force is mw^2r, where m is the mass of the laundry, w is the angular velocity of the spin basket, and r is the distance of the laundry from the rotation axis. The force in g-equivalent would be the mass times the number of g, times, well, g. So the number of g's is w2^r/g. My washer has a spin cycle speed of 640 revolutions per minute (rpm) and I'll assume that my laundry flattens out along the wall of the basket (the inner laundry will experience less g-force) and my laundry basket is 0.25 meters in radius. And g is 9.8 m/s2. Watch out for those units! Number of g's = ( (640 rev/min * 2p/ rev * 1 min/60 sec )2 * 0.25 m )/ 9.8 m/s^2 which is 114.6 g. A handy formula for your home use is 1.119x10^-3 * (spin speed in rpm)^2 * (basket radius in meters).

If you sent your laundry on the space shuttle, it would experience about 3 g's on liftoff. If your laundry had been on the Apollo missions to the moon, it would have experienced about 6 g's on reentry. If you took your laundry to the sun, it would experience 28 g's, and would probably dry really quickly.

Your laundry could get a few g's riding a roller coaster. Alas, roller coasters are limited to 7 or 8 g's. If the g-force is larger than that, so much of your blood is pulled down out of your brain and you black out or die. (The roller coaster marketing people think this is bad for business.) If you are upside-down in a roller coaster, you are limited to about 3 g's: too much blood being forced into your brain makes you "red out," and that's no good either.

But your laundry knows no such restrictions, so why don't you give it the time of its life and send it to University of Colorado at Boulder where they have a mondo centrifuge where your laundry can experience as much as 200 g. You could save up all your laundry too, because this centrifuge can accommodate up to 4000 lbs of laundry! If you only wanted to centrifuge four socks, the KOMPspinTM KA-9.1000 centrifuge gets up to 15,000 g's! But one of the socks vanishes into a parallel universe, just like regular washers.

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