Another (easier) physics question re gravity

[Alex Franke]

Very well explained -- Tom and Anna in particular. Thank you all very much!

And Anna, I sure hope you *don't* "do a better job at staying away from the next physics question" -- I was hoping you would chime in because you explain things very well. (e.g. I hadn't considered tethering Earth -- that example clarifies it quite a bit.)

[JimD]

I did my research before posting this time so I hope to not make embarassing mistakes trying to work from memory. (like I did confusing Bernouli's principle for the ideal gas law)

Earths gravational attraction is due to it's mass and is 32.2 ft/sec2. The mass of the object does not affect it's acceleration. The air resistance normally would - but not in a vacumn. If the ratio of surface area to mass is high (say for a bug), it does not accelerate nearly as fast as something like a lead sinker or a bowling ball.

What changes if you put two huge masses close enough to noticably affect each other is both move. If they both have the same mass as the earth, they would both accelerate towards each other at 32.2 ft/sec2. The large object always moves towards the other object but the effect is not noticable until the masses are somewhat comparable. Most objects on earth have trivial mass compared to the earth but tides happen because of the gravational pull of the moon - smaller but not trivial compared to the earth.

As has been said, anything with a small mass "dropped" towards the earth with an object of huge mass (like the earths mass) would go along for the ride. It could not fall towards one huge object without first moving quickly (32.2 ft/sec2) towards the other closer huge object.

Jim