something to think about while i get this together: the equation we'll be working with here, as you may have guessed, is: the question i want to answer is: how much do i move the earth? by the force of me jumping up and down, how much do i accelerate the earth with each jump? keeping this in mind, it looks like we'll be solving for a in the above equation. we know the earth's mass, and we can make a guess at the force i apply, so acceleration is what we have to solve for. what is the earth's mass? in scientific notation, it's roughly 6 x 1024 kg. if you write that out, it looks like: 6,000,000,000,000,000,000,000,000 kg compared to anything on earth's surface, that's a lot of mass. what about the force i apply to the earth when i jump? i'll put up a page that shows where i got this, but the figure i'll use is 1200 N. to give you some idea where it came from, i weigh 200 lbs. this is roughly equivalent to 90 kg. (90 kg)(9.8 m/s2) gives me a weight of 890 N (N for newtons, that's good enough for me, yeah). now, that's how much i have to push on the earth just to counter gravity equally. if i push with less than that, i fall. if i push with more than that, i jump off. 1200 N is reasonable. it's not enough force to give me an NBA league vertical, but i will leave the ground. putting these numbers in the equation we get: a = 2 x 10-22 m/s2 this is a really tiny acceleration. how tiny? how little is the earth moved by one jumping man? with this much acceleration, it will take over a week for the earth to move the diameter of one hydrogen atom. ducks and rockets |