posted
I was wondering about instantanious changes today and I had a thought. when an object at a high velocity hits a stationary object, and the stationary object is emmbedded in the moving object. does the stationary object's velocity increase instantaneasly?
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the distance over which the acceleration happens is the distance it sinks into the moving object. Once you know the distance and Vf (Vi=0, right?) you should be able to calculate the (very small) time.
edit to add: this works for all collisions, too, in real life, where there is *no* such thing as a perfectly elastic collision. The distance is given by the amount deformity druing the collision, or , alternately, you can just measure the time that the two objects are stuck together...
[ March 22, 2004, 09:57 AM: Message edited by: T. Analog Kid ]
Posts: 2112 | Registered: Sep 1999
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posted
It's an interesting question because common sense says that at some point, the object velocity must increase from zero to another number. Seeing as how at time t = 0 the velocity is 0, and at some future time t = n the velocity is equal to a very high number (assuming relativley in scale masses). However, conventional physics (Newton and on) says that actually there are an infinite number of instants of time between time t = 0 and t = n, no matter how small n is. So you can create a range in which the velocity changes, but the word "instantly" becomes impossible to define since there is no instentanous "now" that exists in the current world of physics.
posted
Unless you are in a Classical Mechanics class with a sadistic instructor, you are much more likely to be given a Force and asked to solve this by Momentum and Impulse.
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posted
Hobbes, I have a friend that is very into the idea that time and space *are*, in fact, in individual units and that the universe is *not* a continuous line, but a number of discrete points so close together that they appear continuous. The idea is that this is the reason for the heisenberg uncertainty priniciple: that we can only measure down to a certain point because nothing smaller exists. He has, much to my chagrin, largely built his life around this theory.
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posted
Is that person me? Seriouly though, I'm a big believer in the discrete universe theory, in fact, I wrote a Cousin Hobbes on it once... I'm not sure I really want to dig it up because it was rather poor writting as I recall, but if you want to search for it be my guest.
He just thinks that Discrete Universe implies a perfectly material one as well... he is a natural determinist based on that and I have seen him make some damned poor decisions because he doesn't feel like he has any choice in the matter. It's a terrible thing to watch a friend abdicate their will.
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posted
When I was at school taking a beginning engineering class, the professor was at the board going through a problem. "So you have a massless rope and two massless, frictionless pulleys...", just the same as we had done dozens of times.
He suddenly stopped, turned around and said "Massless and frictionless pulleys are a little expensive, but here at the University we believe that your education is worth it."
We were kinda stunned because he was not the type to crack jokes. I think that getting married again (he had been a widower for a *long* time) helped him loosen up a bit.
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