4 ms·
So it should not be possible to ride a swing?
by z3t4 7y ago
So it should not be possible to ride a swing?
- knzhou 7y agoIn a swing, the back-and-forth linear momentum comes from the tension in the wires, while the energy comes from your legs. No conservation laws are broken.
- labawi 7y agoIt is not possible to ride an unanchored (and non-couterbalanced) swing in a vacuum.
- steve_taylor 7y agoWhat special properties does an atmosphere confer to a swing?
- gpderetta 7y agoMaybe they meant in 0g?
- dean177 7y agoYou need “downwards” acceleration for a swing. The vacuum bit isn’t important, it’s the gravity. They probably meant 0g rather than vacuum.
- SSLy 7y agonone, but centers of gravity do
- labawi 7y agoIt slows you down :) The vacuum part was an emphasis on requiring a counterpart to change momentum. In an atmosphere you could flap your wings, or use electric fans, and argue what it means to ride a swing, but it would be besides the point, as in an atmosphere there is no need for propellant-less engines from the article.
- z3t4 7y agoIf you can move levers, it's possible to rate your body. Maybe the inertia can be used as an anchor? Or you could use a sail.
- deleted 7y ago[deleted]
- baq 7y agoriding bikes in 0g is also quite difficult, or so i hear.
- Zenst 7y agoA swing would need gravity or some other driving forces for momentum.
- phyzome 7y agoA swing works by moving you back and forth relative to the Earth (and moving the Earth back and forth slightly as well, in the opposite direction, more or less.) The you + Earth system is not actually going anywhere. :-)
- z3t4 7y agoSo you need to leave something behind in order to go somewhere? But it would only be relative to the thing I left behind? But then there is some "special" relativity that applies everywhere?
- phyzome 7y ago> So you need to leave something behind in order to go somewhere? As a definition, no. But no one has been able to figure out reactionless propulsion; as far as anyone can tell, the only way to accelerate in space is to throw something in the opposite direction (matter or light).
- z3t4 7y agoIf you tie a rope to a hammer, then spin it around as fast as you can like a hammer thrower, and drop it. Wouldn't the breaking force propel you in the same direction your let go of the hammer?
- antonvs 7y agoIf you're in zero g and not on a surface with friction to push against, you're not going to be able to do what a hammer thrower can do standing on Earth. But, if you provide some momentum to an object like a hammer and release it, you will move. That goes back to "you need to leave something behind in order to go somewhere."