A question for you all.
Most(if not all) here,will be of the opinion that an inertia drive that provides a uni directional thrust or force in one direction(or most there of),is not achievable-it would break the law of the conservation of energy.But could it just be a case that the law has been misunderstood.
So my question is this--> Who here can accurately explain this law
Every action has an equal and opposite reaction.
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Give an example for each
1-What is the action?
2-What is the equal reaction?
3-what is the opposite reaction?
I want you to think very carefully about Q3.
"Most(if not all) here,will be of the opinion that an inertia drive that provides a uni directional thrust or force in one direction(or most there of),is not achievable-it would break the law of the conservation of energy."
--rather, "of the opinion that an inertia drive that provides a uni directional thrust or force in one direction(or most there of),is not achievable-it would break the law of the conservation of MOMENTUM"
I taught Newtonian mechanics for many years, along with other subjects and would be happy to take a shot at these questions (as I have time).
Newton's third law is basically a re-statement of the law of conservation of momentum.
Consider two masses in space, say an astronaut or spaceman S (mass M) and a space rock R (as big or small as you like, but call its mass m). They are at rest with respect to (wrt) each other, and we (observer) are also at rest. This is selected as a simple case; the momentum of both S and R = zero.
Now the astronaut pushes R away and finds that he moves in the opposite direction. Take the direction of the rock to be the + x direction, then,
Before the push: MV= 0 = mv, and the sum (called the total momentum) = zero
After the push: -MV = mv (equation 1)
and the total momentum is still zero, MV + mv = zero. S has a negative velocity since it moves in the - x direction. (Try not to get hung up on the negative sign, it is a matter of convention trying to keep the directions straight.)
Note that the velocities are equal in magnitude only if the masses are equal. In any case, the equation
-MV = mv allows us to determine the V of the astronaut if we know v of R and the masses M and m.
Inertia is simply an inherent OBSERVED quality in physical objects to resist acceleration. WHY masses resist acceleration (ie., inertia) is not well understood IMHO.
AC - note that your wall is attached to the earth, which is really just a BIG space rock, not fixed. If the astronaut pushes on the wall, he goes one way and the earth goes the other way -- but it DOES move, it is not fixed.
To get the acceleration, assuming the astronaut gives a steady push (constant force), we simply divide both sides of equation 1 by the TIME (duration) during which the push occurs, until contact ends. I will call this t or often we use delta-t, but start the clock at zero and its simply t.
Then, Equation 2 is -MV/t = mv/t .
Now we add a definition of acceleration (constant in this simple case) as velocity/(time interval), and we have
Equation 3 -MA = ma , where A is the acceleration of the astronaut and a is the acceleration of the space rock.
Finally, we follow Newton's second law and recognize that force = mass x acceleration, so that
Equation 4 -F (on astronaut) = f (on the rock), and following from Eq 3 and Eq 4, we can say:
The forces are equal in magnitude and opposite in direction, which is Newton's Third law.
The force on the rock (action) and the force on the astronaut (reaction) -- these are equal in magnitude and opposite in direction. Please note that the action and the reaction ALWAYS act on DIFFERENT objects (i.e., never on the same object).
To be brief (but potentially more confusing IMO):
Every action has an equal-and-opposite-in-direction reaction.
This is Newton's Third Law, and we see how it is derived from conservation of momentum.
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Topic: Inertia Drive (Read 17682 times)
