Matt Jones

**M.Ed., George Washington University**

Dept. chair at a high school

Matt is currently the department chair at a high school in San Francisco. In his spare time, Matt enjoys spending time outdoors with his wife and two kids.

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Gravitational force cannot be simulated, but the illusion of gravity can. All it takes for us to think we are being acted upon by gravity, is a force pulling us against a surface, generally the earth. Because centripetal force keeps an object moving in a curved path, it can make you feel like you're being pressed outwards. While this doesn't replicate gravity, it creates a feeling of **simulated gravity**.

Simulate gravity what is that fake gravity? Well yeah it is, it's fake gravity why we would need simulated gravity? Well if you, an astronaut is going to stay in space for long periods of time the effect 0 gravity is very bad on the body. The body, the muscles weaken and atrophy, the digestive system doesn't work very well things don't get processed the way they should, it's hard to eat and go to the bathroom if things aren't getting pulled down. So you can imagine if you're in space you kind of want gravity around right? So we can simulate gravity by using centripetal force to create that force downwards that feels like gravity okay.

Let's review centripetal force for a minute okay so we can calculate the centripetal acceleration of an object which is the velocity, the linear velocity it's moving divided by the radius okay. The force on that object okay is going to be the mass remember a force is mass times acceleration. So the mass times velocity squared over radius so here is our radius and our velocity in that direction okay. And again simulated velocity since we have a inertia always pushing us away from the center that's going to feel like there's a force going down on us because when we combine these force factors it combines to a force down which kind of acts at centripetal force which is basically the floor of the unit that's revolving pushing us up okay.

Well couple of types of problems you'll be asked about simulated gravity right, they might ask you for example what is the acceleration needed to make something feel like it's gravity or they might ask you the force okay. So let's look at an example of a simulated gravity type of question alright and again this usually relates to some guy in space and he's in a space capsule and we want to give him the feeling that there's gravity there okay. Make his life a little easier a little more like earth okay. So let's say we want to figure out the simulated gravitational force on a 100 kilogram person in space capsule with a radius of 5 meters and a rotational velocity of 10 meters per second. Okay so again they're asking here the force alright not the acceleration this is just the acceleration but the acceleration times the mass will be the force needed okay. So let's solve for that okay so we've got the person who weighs a 100 kilograms okay that person is moving in a tangential velocity of 10 meters per second so that unit is 10 meters per second and that whole unit is squared.

Remember when we solve for that, that actually equals 100 meters per second, meters squared per second squared okay so again with those units remember to square them both and over our radius and our radius is 5 meters of our space capsule okay pretty small space capsule. Okay so if we solve for that we're going to say 100 times 100 is 10,000 meters squared times seconds squared over 5 meters. Okay and again this is kind of confusing so this I can move down here and say second squared and my meter squared here I can cancel the squared with the meters there and now I have 10,000 meters over 5 second squared. And I can simplify that into 2,000 meters per I'm sorry I got my kilograms right I didn't keep my kilograms in here so I'm going to have to keep my kilogram because this is a force not just an acceleration times meters squared over second squared okay.

And remember kilograms times meters over seconds squared equals 2,000 Newtons which is the force that is required to simulate that gravity for that person in space, that's the force that they would feel. Okay and that's how you calculate a problem, to calculated a simulated gravity for someone in space.