Re: physical significance
From: Mr. Cheese (invalid_at_nospam.com)
Date: 12/13/04
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Date: Mon, 13 Dec 2004 12:05:38 -0600
"shashidhar" <shashidhar.a@in.bosch.com> wrote in message
news:cpk4ks$gv2$1@ns2.fe.internet.bosch.com...
> Hello All,
>
> I am a beginner in physics and i am stuck in the following concept i
> found in a book of complex numbers:
>
>
>
> "Consider a child throwing a ball into the air.
>
> For example, assume that the ball is thrown straight up, with an initial
>
> velocity of 9.8 meters per second. One second after it leaves the child's
>
> hand, the ball has reached a height of 4.9 meters, and the acceleration of
>
> gravity (9.8 meters per second2) has reduced its velocity to zero. The
ball
>
> then accelerates toward the ground, being caught by the child two seconds
>
> after it was thrown. From basic physics equations, the height of the ball
at
>
> any instant of time is given by:
>
>
>
> h = (-g*t^2)/2 + v*t
>
>
>
> where h is the height above the ground (in meters), g is the acceleration
of
>
> gravity (9.8 meters per second2), v is the initial velocity (9.8 meters
per
>
> second), and t is the time (in seconds).
>
> t ' 1± 1&h/4.9
>
> Now, suppose we want to know when the ball passes a certain height.
>
> Plugging in the known values and solving for t:
>
> For instance, the ball is at a height of 3 meters twice: t =0.38 (going
up)
>
> and t = 1.62 seconds (going down).
>
> As long as we ask reasonable questions, these equations give reasonable
>
> answers. But what happens when we ask unreasonable questions? For
>
> example: At what time does the ball reach a height of 10 meters? This
>
> question has no answer in reality because the ball never reaches this
> height.
>
> Nevertheless, plugging the value of h = 10 into the above equation gives
two
>
> answers: t = 1+ sqrt(-1.041) and t = 1- sqrt(-1.041)."
>
>
>
>
>
> My question is, in the above example what is the Physical significance of
> the complex time?
>
> I believe this quantity of complex time would be used in some physical
> concept or theory....How do we analyse this complex time in the real
world?
>
If you have an answer for t in complex terms, you made a mistake.
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