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▲ 7734128 7 months ago

You can't turn mass into force, especially not in space.

▲brudgers 7 months ago | parent [-]

For the metrically challenged, pounds are a unit of force not mass.

▲littlestymaar 7 months ago | parent [-]

Wikipedia disagrees with you[1], and if pounds were a unit of weight that'd be very unpractical from a legal PoV to have things being labeled in pounds since the same object have a different weight in Puerto Rico (close to the Equator) and Fairbanks (close to the North Pole).

[1]: https://en.wikipedia.org/wiki/Pound_(mass)

▲delta_p_delta_x 7 months ago | parent | next [-]

To be very pedantic, the pound is a unit of both force and mass, and it's because the unit evolved before the Newtonian understanding of weight versus mass. That's why there exists the pound-mass, and the pound-force.

Of course, in SI this is very straightforward: the unit of mass is the kilogram and the unit of force is the newton, which is the force acting on a mass of one kilogram experiencing an acceleration of one metre per second per second in an inertial frame of reference.

▲brudgers 7 months ago | parent | prev | next [-]

Your comment is ambiguated.

https://en.wikipedia.org/wiki/Pound

▲two_handfuls 7 months ago | parent | prev | next [-]

I distinctly remember reading how I would weigh a different amount on the moon. This only makes sense if the pound is a unit of force.

▲stouset 7 months ago | parent [-]

You would weigh a different amount on the moon, but that is completely independent of how we label our units of measurement.

The pound a unit of force. It is also a unit of mass. Both units share the same name.

▲two_handfuls 7 months ago | parent [-]

It's not independent because if I'm 80kg here, I'm still 80kg on the moon. Because gravity does not affect mass.

If I weigh 160lb on earth I'm told that I would weigh 26lb on the moon.

That makes sense if lb measures force because gravity affects force.

In short, this commonly shared "fact" is consistent with pounds being a unit of force, not of mass.

Or, I suppose, of lb at least sometimes being a unit of force.

▲stouset 7 months ago | parent [-]

If you weigh 160lb on the Earth, you also have 160lb of mass. You would weigh 26lb on the moon and still have 160lb of mass.

I don’t know how to make the point any clearer that there are two units of measurement, both with the same name.

https://en.m.wikipedia.org/wiki/Pound_(force)

https://en.m.wikipedia.org/wiki/Pound_(mass)

▲two_handfuls 7 months ago | parent [-]

So how do I know which is meant in a given sentence?

▲M3L0NM4N 7 months ago | parent | prev [-]

I think it's used as both. Foot-pounds is used as a unit of work, so it's a force in that context.