Curious as to what would happen if I perfectly time it. Would I be safe? Lets say the building is 4 stories high
In: Physics
Good ole’ Einstein can help here with the theory of relativity.
If you’re on a train that’s heading north at 30 km/h, anyone watching the train go by will see you moving at 30 km/h. But then you get up and walk towards the back of the train (south) at 1 km/h, from your perspective you’re moving at 1km/h. Now go back to the guy watching the train (that has windows) and he sees you on the train moving towards the back. His perspective will see you moving 30 km/h north, and 1 km/h south, for a net total of you moving 29 km/h north.
The Mythbusters tested this by getting a cannon that can shoot a soccer ball at 50 km/h, then mounting it on the back of a truck (facing out the back of the flat bed), then fire it while the truck is moving at 50 km/h. The speed of the car and the speed of the cannon countered each other, so it the ball dropped straight down, as the only force not being countered was gravity. It’s pretty neat and I’d recommend watching it to learn about this stuff.
So yeah, when jumping off a bridge that’s falling, you have to take into account the speed you’re falling (you’d be accelerating at 9.8 m/s, btw) and the amount of speed you get jumping up.
You also now have to take into account how forces interact with one another. If you’re in a pool floating on your back, and try to jump horizontally by pushing off an inflatable raft, you’re more likely to just push the raft away without getting much movement yourself. You can push off walls and stuff because the force you’re using isn’t enough to move the wall, so you get flung back.
You’d need to have enough force to make a significant jump that would be enough to counter Gravity’s force on you, but not so much that you’re just pushing the bridge down rather than yourself up. Which btw, is impossible as far as my high school physics education has taught me.
Thing is, if you’re strong enough to jump fast enough to cancel out your falling speed, you’re also strong enough to just absorb the landing without a jump. Landing from a tall building is the same as the reverse, jumping to the top of it.
When the building’s coming down and you’re standing on falling piece, you are not “static” anymore. You’re falling, even if your feet are on still the floor slab that’s coming down.
So if that movement suddenly ends, it’s not different than if you were just falling.
Let’s say it’s a tall building and you gain terminal velocity. So you’re coming down at about 53m/s.
But you jump! Even if you’re in good shape, and your timing is perfect, your jump velocity is about 2m/s.
So you hit ground at 51m/s. What did the jump gain you? Maybe something cool to write on the tombstone. Plus, you’re falling in the middle of debris, probably with a huge chunk of concrete and rebar that pierces your head or something.
In fact, it would have been probably to wiser fall by yourself, and spread your arms and legs apart, air friction would likely slow you more than jumping, and going by yourself would let give maybe a second to choose a softer spot to land to.
For a 4-story building it’s probably wisest to curl into a ball to protect head and neck, it’s not guaranteed death sentence anyway. Also, floor breaks poorer near walls, so I’d stand against a wall, even better if it’s a corner.
I don’t think you can jump off something that is falling because you’d be falling with it. Think how you would jump normally: you start with bending your knees so then when you unbend them you push against the floor. But if the floor and yourself are both in free fall, when you bend your knees there’s nothing to make you stick to the floor, so your torso won’t go down, instead your feet will go up. So then you can’t push against the floor.
Jumping won’t be the deciding factor in your survival, in fact if anything it may hurt your survival chances. That being said, a lot depends on how exactly the building is collapsing. Example that comes to mind – top gear put a truck on top of the building that was being demolished and the truck survived, despite having a cracked frame. That’s not because the truck is amazingly strong, but because if you watch the demolition video – you’d see that the building collapsing does provide a sort of cushion for the roof and it decelerates rather gently. In that kind of impact I’d be more worried about human getting crushed by debris rather than dying from an impact.
No of course not. If the building is collapsing lets say its falling at 40MPH (it’s not ut lets just say). You’re jump “speed” is going to be like, 8MPH (it’s not but lets just say) so you are still hitting the ground at 30MPH+ (you’re not but lets just say). Your puny jump will not outdo the speed you were already falling at. It would be the same as if you were in an elevator that was freefalling 20 floors. Just because you jumped right before impact doesn’t take away from the speed you were already falling at.
No, you wouldn’t be able to accelerate upward fast enough to counter the speed of the fall. Gravity > Jumping.
Acceleration of gravity: 9.8m/s^2 downward.
4 story building takes about 3 seconds to hit the ground.
9.8 x 3 = 29.4 m/s
Human jumping speeds range from 0.5 m/s to 1.5 m/s.
29.4 m/s – 1.5 m/s = 27.9 m/s
You will hit the ground at 27.9 m/s. Pain.
No. Whether you’re standing on something that’s falling or just falling through the air the impact is going to do the same damage to you. Even if you could jump hard enough to significantly slow your fall you will still be exerting a similar amount of force on your body as you would feel when you hit the ground, otherwise the jump wouldn’t slow your fall.
Depends how fast the building is collapsing. Watching demolition videos is seems that it is often much slower than free fall. So you might have a change.
You jumping probably does not matter much in terms of velocity, although if you do have you feet on something heavy, you will be able to “jump” relative to the collapsing building. And it might just save you from being crushed between debris.
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