Would using a bathroom scale be a good way to measure mass in space? Better tool?


Sarah asks:

Determine if using a bathroom scale would be a good way to measure mass is space. If not, recomend a better tool.

Best answer:

Answer by A M Frantz
Scales measure weight. Weight and mass are different quantities, so the answer is no.

A scale would generally measure mass better. However, if you’re in real zero gravity, measuring mass accurately is extremely difficult.

3 thoughts on “Would using a bathroom scale be a good way to measure mass in space? Better tool?

  1. Take the weighing scales – shake them back and forth by hand, noting the force needed to do so.

    Take the unknown object, jiggle it back and forth with the same amplitude and frequency.

    Compare the forces needed to accelerate the two, scale by the (presumably) known mass of the weighing scale.

    It’s not the best method, using a bathroom scale.

    It rather depends on what it is that you’re trying to measure the mass of.

    A person? A spacecraft? A planet? A star?

  2. How can mass be measured in space?

    One gets a clue from clocks, all of which need some sort of device that gauges the passage of time. Pendulum clocks–always kept upright–use gravity, but mechanical wristwatches depend on a balance wheel, turning periodically back and forth–clockwise, then counter-clockwise, then clockwise again–against a spiral spring. Gravity is not involved. Modern electronic wristwatches replace the wheel with a vibrating quartz crystal, acting somewhat like a tuning fork: the motion is much faster, but transistor circuits can easily count the vibrations, which are very stable.

    The frequency of the balance wheel–its number of back-and-forth oscillations–depends on its rotational inertia. Astronauts aboard “Skylab” used something similar–but with a simpler back-and-forth motion, rather than a rotation. It resembled a porch glider, a seat which could glide forward and back against springs.

    Since the oscillation is opposed by inertia, the greater the mass, the slower is the process, and by measuring the frequency of oscillation, a fair idea of body mass could be obtained.

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