Apollo 11 50th Anniversary

[Wes Loewer]

(07-29-2019 04:41 AM)Thomas Okken Wrote:  

(07-28-2019 11:01 PM)cdmackay Wrote:  floating around in the free-fall environment [note I didn't say weightless ].

But they're the same thing. Weight is what happens when something resists the force of gravity, which in freefall by definition does not happen. Now a massless environment, that would be something else.

I've heard that the term "weight" means different things in different countries. American textbooks usually define weight as the force of gravity. In some countries, weight is this resistance to the force of gravity as you described.

For example, say a 100 kg man is in an elevator accelerating upward at a=2m/s^2 on a planet where g=10m/s^2. American textbooks would describe the weight of the man as the force of gravity W=Fg=1000N, while some countries would describe his weight as the normal force W=Fn=1200N. American textbooks often refer to this normal force as the "apparent weight" as in "your real weight is 1000N but it would feel like you weigh 1200N."