Catie Helm writes:
> I'll cheerfully invite correction for any of the
> REAL physicists out there... ;-)
I'm not a physicist, but I play one on the net... :-)
> I think it is possible, perhaps, that you have confused velocity and
> force? The force that a grav belt would put out would have to be
> variable. Otherwise, there would be no control on velocity! Recall
> that force is (mass x acceleration). If the force is always constant,
> then there would always be constant acceleration and ever increasing
> speed (assuming, of course, that the grav belt force exceeds g...). I
> think you must have misstated yourself :-) because to achieve a
> constant velocity, you must accelerate (ie you must use a force
> greater than the forces opposing you, which in this case are drag and
> gravity) and then having achieved your desired velocity, the force
> then must decrease to match the opposing forces such that the desired
> velocity is maintained.
Ah, but you just got through telling us that *drag is velocity
dependent*! So clearly the prior poster *meant* constant
*maximum horizontal force* exertable by the grav belt. Assume
for example that at most the grav belt can put out a constant
force which will accelerate the wearer horizontally from a
standing start at 1G. Will the wearer keep accelerating
indefinitely? No, the wearer will stop accelerating when the
reach *exactly terminal V*. With twice as much force, one can
go somewhat faster, but not quite twice as fast, since drag is
actually nonlinear. However if you use the H&R approximation
you quoted, then a grav belt with twice the force will achieve
twice the max V of our example grav belt above.
Me, I think I'll stick to walking -- heights make me giddy.
Bart Massey
[email removed]