
Originally Posted by
drone
If weight is strictly a function of gravitational force, then no. But I would imagine that if you put 1kg of lead on a (force)scale at sea level in NYC, it would weigh X lbs, and the same 1kg of lead at sea level in Rio would measure X-Y lbs, where Y is a small number.
Seems that you would imagine correctly.
Technically, whenever someone stands on a balance-beam-type scale at a doctor’s office, they are truly having their mass measured. This is because balances (“dual-pan” mass comparators) compare the weight of the mass on the platform with that of the sliding counterweights on the beams; gravity serves only as the force-generating mechanism that allows the needle to diverge from the “balanced” (null) point. Balances can be moved from Earth’s equator to the poles without spuriously indicating that objects gain over 0.3% more weight; they are immune to the gravity-countering centrifugal force due to Earth’s rotation about its axis. Conversely, whenever someone steps onto spring-based or digital load cell-based scales (single-pan devices), they are technically having their weight (force due to strength of gravity) measured. On force-measuring instruments such as these, variations in the strength of gravity affect the reading.
So the centrifugal force of Earth's rotation really does affect how much mass weighs. Just very, very slightly. Good to know.
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