# The Naked Scientists Forum

### Author Topic: What weighing scales would still work on Mars?  (Read 1592 times)

#### thedoc

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##### What weighing scales would still work on Mars?
« on: 18/03/2014 21:59:14 »
Here is a great "mind puzzle". For many years I used one of those flat scales with an internal spring but finally decided I couldn't trust the damn thing: if it looked like I'd gained a couple of pounds, maybe the spring had gone soft!

So finally I got a scale that uses counter-balance weights that you slide along an arm to get really precise measurements. Just this morning it occurred to me: what if I was on Mars, where the gravity is much weaker than here on Earth?

Obviously with weaker gravity scales with an internal spring would give grossly inaccurate results, since they measure only the pressure of your body pressing against the spring.

But here's the amazing fact: on Mars the counter-balance scale would still work perfectly, since the weakened gravity would pull with equal force against you and the counter-balancing weights. Of course you would "weigh" less, but since your mass remained the same, you would get accurate readings for what you would weigh on Earth!
John Gamel
Asked by John Gamel

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« Last Edit: 18/03/2014 21:59:14 by _system »

#### syhprum

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##### Re: What weighing scales would still work on Mars?
« Reply #1 on: 12/03/2014 10:07:21 »
Although the logic sounds impeccable I have slight doubts as to whether the ratio of the mass of the bar compared to that of the fine adjusting sliding weights might have a disturbing effect, can someone put my mind at rest or should I take a set of weights for calibration.

#### chiralSPO

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##### Re: What weighing scales would still work on Mars?
« Reply #2 on: 12/03/2014 15:34:40 »
As long as there is a built-in counterbalance for the arm, and not just an adjustment in the scale, a mass-balance scale should function in most homogeneous gravitational fields

#### syhprum

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##### Re: What weighing scales would still work on Mars?
« Reply #3 on: 12/03/2014 20:42:56 »
I'm glad you said homogeneous I was thinking there might be a problem close to small black holes

#### The Naked Scientists Forum

##### Re: What weighing scales would still work on Mars?
« Reply #3 on: 12/03/2014 20:42:56 »

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