Why does Rocket Go Up ?
Professor Feynman was teaching the class.
"Even from students of physics one may often hear a totally wrong explanation of a rocket's flight. They claim that it goes up by thrusting itself away from the air with the help of gases formed from gunpowder combustion. That incidentally is what ancients thought-rockets are invented long, long ago."
He added "But if we were to fire a rocket in an airless void it would fly, and even better than in the air."
What's the right explanation ?
"Even from students of physics one may often hear a totally wrong explanation of a rocket's flight. They claim that it goes up by thrusting itself away from the air with the help of gases formed from gunpowder combustion. That incidentally is what ancients thought-rockets are invented long, long ago."
He added "But if we were to fire a rocket in an airless void it would fly, and even better than in the air."
What's the right explanation ?
Labels: friday special, funphysics, thinktank
posted by Rajesh Lal at
6:10 AM
8 Comments:
The expansion of gas caused by the ignited feul creates pressure which only has one way to exit, through the bottom. This is called thrust.
Newtons Law: Every action has an equal and oppisite reaction.
Since the action of thrust (energy exiting the bottom), the rocket must do the opposite. Doesn't matter if it's in space or in the atmosphere. The only difference is that in space there is no resistance to deal with (air & gravity).
danr got there before me Euclid
Technically, that is not how it really works.
Yes, it is true that it is called thrust…however, it is not due to “pressure”
When the fuel ignites, the combustion goes in ALL DIRECTIONS, not just down.
Therefore, particles are going UP and hitting the rocket from the inside. Each particle would hit the rocket and then bounce back (goes out of the end afterwards)…
Yes, Newton’s third law still applies, but the conservation of momentum is more of a factor. If are particle is initially going up (one unit of momentum), and hits the rocket and then bounces back. That means that there must have been 2 units of momentum transferred to the rocket in order for the momentum of the overall system to be conserved
~Cybersurf~
you dont understand the laws of physics at all, do you cybersurf?
for the particles to accelerate up into the rockets base, then the force of the particles accelerating upwards would equal the force of the impact to the bottom of the rocket. that means the force pushing the rocket down would equal that pushing it up.
The right explanation is that the writer of this riddle should check his grammar.
"The Rocket Go up" is not a sentence. Nice try, lovey.
lets say that the particles can go 4 different ways for simplicity.
left, right, up and down.
the particles that go left or right would cancel each other out when they hit the sides of the rocket.
the particles that go down would go straight out of the rocket doing nothing to propel the rocket.
the particles that are going up, would hit the rocket would transfer its momentum to the rocket pushing it forward.
~Cybersurf~
ok, i only have a high school education seeing as I just graduated. I haven't even took physics or ne thing. but ne ways this is what I am thinking. The rocket fuel ignited and it is pointed downwards due to a nozzle thus forcing the rest of the rocket to be pushed in a upwards motion. not really in a upwards motion but more in a forwards motion. seeing as the rocket goes where it is pointed for the most part, wind conditions can blow it off course a bit i suppose.
i thought fire needed air to burn
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