The Lee-Tseung Lead Out Theory

[Top Gun]

Quote from TopGun

"Dear utiliarian,

I believe you already know that air cushions or padded surfaces are used in fire fighting - allowing the persons to jump from a few floors.  The purpose of such padding is to reduce the force and absorb the energy."

I can't believe this statement above.  You know even less about physics than I thought.  The purpose of such padding is NOT to reduce the force, the force is the same.  The only thing padding does, as does the crumple zone in vehicles, is to space the force out over a longer period of time.  That is all.  The net force is the same.  It is always the same.  A person jumping from a building hits the padding with the same force as if he hit concrete.  The only difference is that the sudden deceleration is spread out over a longer period of time which allows him to survive.  This is high school physics here TopGun.  Energy can not be created nor destroyed. (Nor absorbed)  Remember, it is time that is the only difference.

Bill

Dear Bill,

Please read your elementary physics books again.

Force = Rate of Change of Momentum

At the moment of impact, the person will have a certain momentum (mass x velocity).  We need to reduce the velocity to zero with the longest time.  In Physics terms, this is reducing the force.

[hansvonlieven]

Dear Bill,

Please read your elementary physics books again.

Force = Rate of Change of Momentum

At the moment of impact, the person will have a certain momentum (mass x velocity).  We need to reduce the velocity to zero with the longest time.  In Physics terms, this is reducing the force.

He doesn't get it, does he?

Hans von Lieven

[Top Gun]

Let me spell out the physics of air cushion or padded surface clearly for the non-physicists.

At the moment of impact, the velocity is v, the mass is m.  The momentum is mass x velocity or mv.  We want to reduce the velocity to 0.  We cannot do anything about the mass.  Thus the change of momentum is (mv -m0).  If the time taken is t, the force is rate of change of momentum or:

F = (mv-m0)/t
    = mv/t

The purpose of the air cushion or padded surface is to prolong t.  If t is longer, F will be smaller.

This is basic physics and cannot be wrong.  Those who cannot understand such basic physics should not post rubbish and make fools of themselves.

[spinner]

I see someone scored a point. 

Check out "Collision". Elastic, inelastic and plastic.

Cheers!

[Devil]

The two prayers to me are:

The lead-out-energy from a pendulum is equal to the vertical component of the tension of the string multiplied by the vertical displacement.

and

A propulsion system can be produced from unbalanced forces generated within.

Recite them 666 times.