Can inertia be used as a force for propulsion?
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What you’re suggesting is basically how you play pool – you hit the white ball, and the white ball must hit the other balls to propel them into the holes. While it clearly works in pool, it is a rather violent method of getting things moving and a spaceship isn’t going to appreciate a launch by having something slam into it. The impact is just as likely to cause major structural damage as it is to make it move.
It’s a little unclear what you mean, but the answer to the most obvious interpretation is “no”.
Specifically, inertia is the statement that the momentum of an object doesn’t change unless a force is exerted on it, and propulsion is, roughly, a change in momentum.
It depends on what you mean.
So the answer could be no if you are using inertia to mean “the tendency for objects velocity to remain unchanged unless acted upon by and outside force” and if by propulsion you mean “the force used to change the velocity of an object”
Because with those definitions your question is basically “Can we use the fact that objects don’t change velocity to get them to change velocity?” To which the answer is no, that doesn’t even make a lot of sense.
However, if you are using a more colloquial definition (which you really should never use in a professional context) of “this object has inertia because it’s moving” which is basically just kinetic energy then yeah that’s basically how all propulsion works. You take a moving object and smack it into another object that isn’t moving the way you want it to.
Take a big heavy flywheel in a cradle, spin it like mad and it’ll build up a lot of inertia.
If should be able to spin for quite some time as a storage method, but there will be losses.
Drop that flywheel down a bit so it contacts the ground, and then it’ll act as propulsion.
It’s not going to work in space but you can figure out something clever, like I guess if you could get that flywheel to impact a captive mass in a confined tube, it should be able to propel the mass down the length until it hit the end, and then kicks the entire gadget forwards in that direction.
Inertia is not a force. Inertia is the result of a force being (or not being) applied.
Something can be propelled and then under inertia, remain in motion… But inertia itself would not act on something.
If one thing collides with another thing, its kenetic energy becomes the force that is transferred into another object, acting upon it and changing its state of inertia.
Inertia is what keeps that first object moving and the second object at rest.
Inertia merely states that an object in motion will keep moving unless it is stopped and an object that is not moving will not move unless something makes it move.
Since inertia is not a force, it cannot be used to propel or accelerate. Things are propelled or accelerated or decelerated to change their inertial state.
You could make a flywheel car. Spin up its flywheel at home, using cheap electricity, then drive it around, sapping energy from the flywheel, before getting back home.
You’ll lose most of the energy to losses in bearings, you couldn’t drive it very far, accelerating would be very difficult die to the vehicle wanting to gyroscopically remain stationary when you take off, and in a crash that huge flywheel would alive through everything and probably harm a lot of people. But… It could be done.
Yeah. A flywheel.
You get a large, heavy wheel spinning and it will keep spinning for ages.
There are losses from friction, but it is a way to mechanically store energy.
One was used for a little while in the ANU in Canberra, Australia to power the particle accelerator. It wasn’t a great idea, as it was used to accelerate sodium, which ended up with debris flying everywhere and blinding a poor lab assistant. The flywheel itself is still on the campus as part of an artwork out the front of a physics building
I’m not exactly sure what your question means specifically, but jumping is an example of using inertia to creation propulsion. the earth is massive and has a ton of inertia, so when you push against it to jump, the earth stays put, and you push off of it and propel yourself into the air. (technically the earth does move, but by an amount that I think would be just about impossible to measure)
but I think you might mean if you’re floating in the middle of space, if you can use inertia to “swim” through space? other than the whole suffocation and freezing to death part, it’s possible yes to use inertia to create propulsion. but it’s not free, and you’re expending energy to create the movement
No, inertia is the resistance to change in motion, not a force the closest thing you could do to this is have a heavy object hit a small object at a low speed, sending the small object off at a high speed, but this is just conservation of momentum, not using inertia as a force.
You can do that yourself if you hold a tennis ball on top of a basketball and drop both at the same time. When it bounces, the tennis ball gets rocketed up, and the basketball barely bounces at all.
A rocket also does a similar thing. It sends the fuel backwards very fast so the rocket can go forwards, but again, this is just conservation of momentum.
There is [Spinlaunch](https://www.space.com/spinlaunch-aces-10th-suborbital-test-launch), which is a hilariously awesome way to send something to space, but I’m not sure if it counts.
There’s the reaction wheels that are used on a lot of satellites to keep them pointed in the right direction without having to use up fuel, but that one isn’t really propulsion.
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