Good navigation skills, not so much for Inverse Kinematics (calling second elevator).

3 more comments have been lost in the ether at this killed duplicate.

If a solution is posted on the internet and everyone calls you an idiot, is it still a solution?

Rick figured that although a nut traveling DDWFTTW might be the simplest form of such a device, replacing the threaded rod with a wheeled vehicle would be more compelling – and possibly even less intuitive. He conceptualized replacing the device’s keel nut with gearing from a drive axle to a propeller shaft that would replicate the kinematic constraint perfectly. With the problem solved as far as he was concerned, he posed the new brainteaser on two internet forums, one for radio controlled helicopter pilots, the other for kitesurfers. Given the solution, Rick imagined people would find this clever.

Instead they considered him an idiot for ever imagining such a thing to be possible.

This is where the pointless brainteaser took on a life of its own. Science, physics and aerodynamics forums exploded. Sailing forums exploded. Flying-related forums exploded. It was silliness traveling at the speed of electrons. Turns out it’s serious business when someone is wrong on the internet, and boy did the internet ever believe Rick was wrong.

One interesting factoid emerged from the chaos. We learned that a Michigan University student posed this same non-problem – and a solution identical to Rick’s — in the 1940s. The student’s paper surfaced at Douglas Aircraft in the 1960s. Apollo M.O. Smith, the company’s chief aerodynamics engineer, and wind tunnel engineer Dr. Andrew Bauer went at it like Rick vs. the Internet. Bauer said it would work. Smith wasn’t convinced. Bauer bet Smith a dollar and went to work.

Read More http://www.wired.com/autopia/2010/08/ddwfttw/all/1#ixzz0y2H81thY

>> ^rottenseed:
>> ^oxdottir:
I think you need quite a tall rooftop for this to be true.
>> ^rottenseed:
The harder thing to understand would be if I told you that if you fired a bullet from a rooftop straight down to the ground, or you fired it at an upward angle, due to the conservation of energy, both bullets would have to be travelling at the same velocity magnitude when they hit the ground (although direction at impact would be different, obviously).


nope...be it an inch or 100 stories
Ug + KE(initial) = KE(final) for both scenarios the potential energy do to being on a roof and the velocity of the bullet leaving the gun are the same. As long as the mass of the bullets are the same, it'll land with the same velocity. (Trust me when I first heard that I did the brute force kinematic equations to solve this problem and it is in fact the same velocity.)




No. The longer a bullet is in flight, the more air resistance has affected it. The one fired at the ground would get there quicker, thereby retaining more of the energy imparted on it by the exploding gunpowder.

>> ^rottenseed:
>> ^oxdottir:
I think you need quite a tall rooftop for this to be true.
>> ^rottenseed:
The harder thing to understand would be if I told you that if you fired a bullet from a rooftop straight down to the ground, or you fired it at an upward angle, due to the conservation of energy, both bullets would have to be travelling at the same velocity magnitude when they hit the ground (although direction at impact would be different, obviously).


nope...be it an inch or 100 stories
Ug + KE(initial) = KE(final) for both scenarios the potential energy do to being on a roof and the velocity of the bullet leaving the gun are the same. As long as the mass of the bullets are the same, it'll land with the same velocity. (Trust me when I first heard that I did the brute force kinematic equations to solve this problem and it is in fact the same velocity.)

If I'm not mistaken, this also holds true for a bullet fired at a downward angle as well. (Since the upward angle bullet eventually becomes an identical downward angle bullet once it crosses back beyond the level from which it was fired.)
Of course, the confusing thing in the problem, if I understand correctly, is that velocity magnitude at impact is identical, while downward velocity will be less for the angled bullet.

>> ^oxdottir:
I think you need quite a tall rooftop for this to be true.
>> ^rottenseed:
The harder thing to understand would be if I told you that if you fired a bullet from a rooftop straight down to the ground, or you fired it at an upward angle, due to the conservation of energy, both bullets would have to be travelling at the same velocity magnitude when they hit the ground (although direction at impact would be different, obviously).


nope...be it an inch or 100 stories

Ug + KE(initial) = KE(final) for both scenarios the potential energy do to being on a roof and the velocity of the bullet leaving the gun are the same. As long as the mass of the bullets are the same, it'll land with the same velocity. (Trust me when I first heard that I did the brute force kinematic equations to solve this problem and it is in fact the same velocity.)

>> ^silvercord:
Phrase of the video: "It couldn't fire its payload beyond the range of the resulting nuclear fallout."
Shoot and run like hell.

It really makes an understanding of geometry and kinematics an important issue

Will do. I was having a cigarette the other night and turned to my right and saw a possum pokin' around in my bushes. It made me think of your little possum face.

Which physics is it? Kinematics (Newtonian)? If so I'm sure myself or plenty of other sifters could be of service.

In reply to this comment by moodonia:
Hey Rottenseed Congratulations!
That some pretty severe stuff your doing (which I wont pretend to understand) you should be proud, especially if your working. I too am trying to work and do a degree and its kicking my little butt. Currently waiting to hear how badly I failed my physics class by... Repeats in August, fingers crossed!

Have a nice drinkie to celebrate!