Space rod question..
Discussion
A 'fun' question....
I'm traveling in my space ship in interstellar space and I approach a LONG metal rod.
This metal rod is 1 light year long.
I get out of the ship and give it a push (in the direction of its length) - then get back in to my ship.
The question is : if I then set off in the space ship is it possible for me to reach the other end of the rod before it starts to move ?
I'm traveling in my space ship in interstellar space and I approach a LONG metal rod.
This metal rod is 1 light year long.
I get out of the ship and give it a push (in the direction of its length) - then get back in to my ship.
The question is : if I then set off in the space ship is it possible for me to reach the other end of the rod before it starts to move ?
Atomic12C said:
A 'fun' question....
I'm traveling in my space ship in interstellar space and I approach a LONG metal rod.
This metal rod is 1 light year long.
I get out of the ship and give it a push (in the direction of its length) - then get back in to my ship.
The question is : if I then set off in the space ship is it possible for me to reach the other end of the rod before it starts to move ?
If your space craft can exceed the speed of sound in your metal rod, and ignoring how long it takes to accelerate to that speed, yes; otherwise no.I'm traveling in my space ship in interstellar space and I approach a LONG metal rod.
This metal rod is 1 light year long.
I get out of the ship and give it a push (in the direction of its length) - then get back in to my ship.
The question is : if I then set off in the space ship is it possible for me to reach the other end of the rod before it starts to move ?
Good answer.
This would seem to be the most popular result.
Given such questions that one often finds on the internet there are a lot of assumptions that you make to arrive at any particular answer.
For example, another popular answer is that due to the length of the rod and its mass, a push by a human in a space suit would result in an undetectable movement on the rod. The human would simply push himself backwards ;-)
Another answer maybe that as the rod is not constrained in all 3 dimensions any push and resultant deformation would be 'damped' out within a certain length of the rod. ie. the force would not be transmitted all the way to the end of the rod, instead it would result in a widening of the rod as the atoms are pushed together and the rod expands in diameter.
But either way, and what ever your assumptions, it made me think about it for a while.
This would seem to be the most popular result.
Given such questions that one often finds on the internet there are a lot of assumptions that you make to arrive at any particular answer.
For example, another popular answer is that due to the length of the rod and its mass, a push by a human in a space suit would result in an undetectable movement on the rod. The human would simply push himself backwards ;-)
Another answer maybe that as the rod is not constrained in all 3 dimensions any push and resultant deformation would be 'damped' out within a certain length of the rod. ie. the force would not be transmitted all the way to the end of the rod, instead it would result in a widening of the rod as the atoms are pushed together and the rod expands in diameter.
But either way, and what ever your assumptions, it made me think about it for a while.
The "speed of sound" answer sounds entirely reasonable for very small displacements.
What about larger displacements, i.e. many times larger than the distance between the molecules in the lattice? Would the rod simply bulge out to accommodate the compressed volume and the bulge travel down the rod at the speed of sound?
What about larger displacements, i.e. many times larger than the distance between the molecules in the lattice? Would the rod simply bulge out to accommodate the compressed volume and the bulge travel down the rod at the speed of sound?
Mr2Mike said:
The "speed of sound" answer sounds entirely reasonable for very small displacements.
What about larger displacements, i.e. many times larger than the distance between the molecules in the lattice? Would the rod simply bulge out to accommodate the compressed volume and the bulge travel down the rod at the speed of sound?
Yes true.What about larger displacements, i.e. many times larger than the distance between the molecules in the lattice? Would the rod simply bulge out to accommodate the compressed volume and the bulge travel down the rod at the speed of sound?
Another result could be that as the molecules in the rod would not be in exact linear alignment, any push would not create a 100% aligned force transmitted along the entire length of the rod, so at some point the initial displacement made by the push on one end would eventually be dampened out by a 'buckle' or non-linear movement in the rod.
Atomic12C said:
I get out of the ship and give it a push (in the direction of its length) - then get back in to my ship.
You wouldn't be able to get back in the ship because almost all the force you put into trying to push the rod sent you in the opposite direction.You should have pushed it with your spaceship...
Gassing Station | Science! | Top of Page | What's New | My Stuff