| Topic: |
Science > Physics |
| User: |
"Peter" |
| Date: |
21 Apr 2006 10:42:06 AM |
| Object: |
Work - impulse |
Hi, I understand that an impulsive force can do work; As a matter of
fact, I don't think there is any doubt about it. But, impulse = Ft,
whereas work = Fx. Isn't there an incompatibility here? What am I
missing? Could someone please explain? Thanks.
Peter
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| User: "Mike" |
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| Title: Re: Work - impulse |
29 Apr 2006 08:29:57 AM |
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Peter wrote:
Mike, my finding is that only a change in the magnitude of the relative
velocity of an object can produce a change in its kinetic energy.
I do not understand your statement. You are stating things in a
peculiar way. It is a simple fact that if the relative velocity of a
body changes so is its KE wrt a FoR. I do not see what is this use of
the word "produce". Are you once again looking for mechanisms? That is
not a subject of mechanics.
But
the same amount of force, work, or impulse can produce different
amounts of change in the magnitude of the velocity of the object,
depending on its mass.
Again, this is a peculiar statement. It is a simple fact that KE is a
function of mass m as in KE= mv^2/2. What "produces" what is not a
subject of mechanics.
Tie a rock to a string a rotate it above your head. There is a
centripetal force F on the rock and the changes in momentum are
directed towards the center of rotation. Either one of the following
propositions is good in mechanics:
p1: the motion of the rock gives rise to the centripetal force
p2: the centripetal force gives rise to the motion of the rock
Either one, p1 or p2, is good for the purpose of analyzing the motion
of the rock. If you care about what "produces" what you must ask for
help from a guru or priest who claims to know the ultimate causes of
things.
Your statements came continuously to reinforce my initial suspicion
that you are only interested in final causes, not so much in mechanics.
if that is true, you will not find any help fro physicists and you are
alone in this metaphysical journey of yours.
Mike
Peter
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| User: "Peter" |
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| Title: Re: Work - impulse |
29 Apr 2006 04:12:10 PM |
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Mike, my finding is that only a change in the magnitude of the relative
velocity of an object can produce a change in its kinetic energy.
I do not understand your statement. You are stating things in a
peculiar way. It is a simple fact that if the relative velocity of a
body changes so is its KE wrt a FoR. I do not see what is this use of
the word "produce". Are you once again looking for mechanisms? That is
not a subject of mechanics.
O. K., I'll omit the word "produce." I can say: "My finding is
that only a change in the magnitude of the relative
velocity of an object can change its kinetic energy." Same thing.
But
the same amount of force, work, or impulse can produce different
amounts of change in the magnitude of the velocity of the object,
depending on its mass.
Again, this is a peculiar statement. It is a simple fact that KE is a
function of mass m as in KE= mv^2/2. What "produces" what is not a
subject of mechanics.
Again too, I can change it to: "The same amount of force, work, or
impulse can change differently the magnitude of the velocity of an
object, depending on its mass." Is it better?
Your statements came continuously to reinforce my initial suspicion
that you are only interested in final causes, not so much in mechanics.
if that is true, you will not find any help fro physicists and you are
alone in this metaphysical journey of yours.
No, I am not interested in final causes. I know physics does not deal
with that. I am talking about physics problems.
Peter
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