The physics of walking

[KITT222]

I think this might be a variant of of whats up there, but I think people push off of the earth. If the earth were to push back, than what would happen if I had a friend walk away from me in the same line? Its just confusing the way its phrased.

[Bicycle Bob]

Try imagining that you are on a space walk, and have a heavy weight on one hand. If you push it away, your combined center of gravity stays in the same place, so you move away from it also. If you are dealing with a satellite that weighs the same as you, both objects would move the same amount. If you grab the space station, you do most of the moving, but it still shifts.
So when you raised your hand in class, the earth moved away from your hand a tiny amount, and also slowed it's rotation due to increased moment of inertia. The theory is easier than the physical measurement of the extreme example, though.

J.E. Gordon has some choice paragraphs on how floors push up on your feet in "Structures." Also a cartoon, captioned "Do stop pulling on kitty's tail, darling!" "I'm not pulling, mummy, kitty's pulling!"

[thatguitarguy]

I don't know how many other people notice it, but I find it much easier to walk in an Easterly direction because it is counter to the Earth's rotation.

I'm thinking that there are enough people on this planet that if we all got organized we could all walk to the West at the same time and slow the planet down to make the days longer.

[theycallmeebryan]

Bob explained it about as easily as it comes....

so kiddies, if you ever find yourself floating away from a spaceship in space and you happen to have a tool with great mass in your hand, throw that tool in the direction opposite the spaceship and it will either slow your movement down (if you have more mass) or will allow you glide back back to the ship (if the tool has more mass).

[NiHaoMike]

The force will act on both objects. With two objects of the same mass, they would accelerate at the same rate but in opposite directions. Let's suppose Allie and Shannon each have a mass of 50kg, and they're ice skating, so let's neglect friction. If they start from a standstill and they push each other away such that Allie has a final velocity of 1 m/s North, Shannon would have a final velocity of 1m/s South.

If the same situation happened but with Mike (75kg) instead of Shannon, Mike would have a final velocity of 0.667m/s South. With Jean (150kg), she would have a final velocity of 0.333m/s South. If there was a 1500kg car (in neutral, neglecting friction and angular momentum) instead of the other skater, the car would have a final velocity of 0.033m/s South.

Finally, let's have Allie push against a wall that is firmly attached to the earth (6x10^24kg). The change in the earth's surface velocity would be 8.3x10^-24m/s. That is insignificant enough to be impossible to measure. Therefore, it is neglected.

It feels like PHYS 218 all over again...

[bgd73]

your science teacher drives a front wheel transverse drivetrain. It brings a disease to teachers as well.

weirdo.

he forgetting we got two legs attached to the hip, attached to a central nervous system...attached to...

a bit more than a foot is happening to walk, we kill most of the energy away with a pendulum of balance, before even moving forward, unless sprinting like a steroided olympic runner...or an inline four....
you know 200% more effort for 20mph faster rather than torquing balance.


the same two feet could be pumping a gear ratio on crank...for 40mph faster...
linear to revolution, it is sOOOOOOO confusing for people who end up in charge of it's engineering.

not to be evil. We all got a path. me typing with two fingers for example..highly unlikely pc builder, and runner...

those that do get a real balance through thier heads end up the leaders for a long time, nameless.
how is that good for marketing eough food for 1 billion people?
god comes down like a haitian eartquakle eventually. stand leaders stand.

[pstrbrc]

Originally Posted by thatguitarguy

I don't know how many other people notice it, but I find it much easier to walk in an Easterly direction because it is counter to the Earth's rotation.

One would think that where you live, walking south would be easier, north harder. (Isn't it downhill from Leadville to Buena Vista on US 24?)

[Piwoslaw]

I levitate.