Ænigma Guild

Yume wrote:

Snow wrote:Here's another follow up teaser:

Now suppose the planes engines were off and that it was loaded with cargo in the front of the plane. The planes captain takes all the cargo and moves it to the very back of the plane. An observer standing next to the treadmill watchs. Does the observer see the plane move?

The way I see it is the cargo has to achieve some sort of velocity to get from the front to the back. If the cargo were pushed (frictionless) from the front of the plane at a certain velocity and then had a nonelastic collision with the back wall of the plane, the plane would have a force pushing it forward meaning that if it were on a runway it would move forward then stop (net kinetic energy gain = 0, net potential energy gain = 0).

But instead of sitting on a runway it's sitting on a treadmill that moves in the opposite direction of the plane. However we've previously determined that any motion of the treadmill has zero force on the plane because the plane still uses ball bearing wheels. So the only forces on the plane are pushing it forward as the cargo heads to the back and then pushing it back as the cargo hits the back of the plane meaning that the plane is displaced relative to the observer, starting still and ending still.

kkay wrote:Ah, but a FBD by itself may indicate motion, but it does not exactly mean that the object has to have movement relative to the system. In your description, assuming we changed it from a plane to a simple block on a treadmill, the force of "thrust" would create acceleration and movement in the block, which is then transferred 100% to the treadmill, meaning the treadmill would accelerate relative to the force. The block experiences no net movement.

I didn't know how jet engines worked exactly, but I figured it was a force applied against the pressure of the air right behind the engine, sorta like if you attach a balloon full of air to a straw with a thread through it, the balloon will move opposite of the direction the air inside is moving due to differences in pressure. Hence why I asked how the engine worked. If I had thought of it as moving in regards to how a propeller plane would move then I would have had a different answer.

Lyion wrote:fuck i missed it, because all girls were dressed like sluts oh ya.

manx wrote:a. the tires will burn off and it will shoot off the back of the treadmill

b. the tires can handle unthinkable amounts of wear and tare and it will roll off the front of the treadmill.

since the wheela are working against the treadmill and the engines are working against nothing but air, wouldnt the wheels reach like a rotation lvl of infinity and then wouldn't the plane shoot off the front of the treadmill?

*edit- just thought about it a bit more, it would look just like a plane taking off on a solid surface speed wise.... the only way to keep the plane stable would involve the use of a wind tunnel to counteract the engines or whatever, which isnt part of the question... so my final answer is no, the this equation cannot exist in a perfect world! I think snovv pointed out that this equation would be much more interesting if the plane was propelled by its wheels.