Are g or kg ever a proper unit for weight? A = YES

<div class='quotetop'>QUOTE(NoMoShocks @ Sep 13 2007, 01:31 PM) [snapback]511963[/snapback]</div>

Ah, but that depends on which orbit it's in. In Low Earth Orbit, the gravitational field of the Earth is not much weaker than on the surface (about 90%), so the force (centripetal force/weight) is nearly the same, but because it's in free-fall, the apparent weight is zero. At a more distant orbit (such as say, geostationary at 36000 km), the gravitational force is significantly weaker (about 2% from my back-of-the-envelope calculation here).

Yes, I think they should be, but if they haven't been distinguishing between weight and mass, why should they start getting pedantic now? (It looks like something that probably passed the spell check test and was left)

 

<div class='quotetop'>QUOTE(NoMoShocks @ Sep 13 2007, 01:31 PM) [snapback]511963[/snapback]</div>

Ah, but that depends on which orbit it's in. In Low Earth Orbit, the gravitational field of the Earth is not much weaker than on the surface (about 90%), so the force (centripetal force/weight) is nearly the same, but because it's in free-fall, the apparent weight is zero. At a more distant orbit (such as say, geostationary at 36000 km), the gravitational force is significantly weaker (about 2% from my back-of-the-envelope calculation here).

Yes, I think they should be, but if they haven't been distinguishing between weight and mass, why should they start getting pedantic now? (It looks like something that probably passed the spell check test and was left)

 

The best way to address this is as follows:

Q: "A 60 kg Astronaut weighs 60 kg on earth. How heavy would the Astronaut feel on the moon?"

A: "On the moon, a 60 kg Astronaut would feel like 10 kg."

It feels like 10 kg, but is actually 60 kg. This addresses the idea in the student's mind that the Astronaut's mass never changes. The idea is implied, and can (correctly) solidfy the idea of unchanging mass without addressing it. Also, the "feels like" leaves wiggle room for later, and again correctly implies that it's only a feel, not the true mass.

Nate

 

The best way to address this is as follows:

Q: "A 60 kg Astronaut weighs 60 kg on earth. How heavy would the Astronaut feel on the moon?"

A: "On the moon, a 60 kg Astronaut would feel like 10 kg."

It feels like 10 kg, but is actually 60 kg. This addresses the idea in the student's mind that the Astronaut's mass never changes. The idea is implied, and can (correctly) solidfy the idea of unchanging mass without addressing it. Also, the "feels like" leaves wiggle room for later, and again correctly implies that it's only a feel, not the true mass.

Nate