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- Thread starter reddevil2576
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How can you make space travel available to everyone when you don't even understand newtons second law of motion?

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berkeman

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dp/dt is the calculus representation for the change in momentun per unit time. p = mv is the linear momentum, with m = mass and v = velocity.

It would be good for you to find a basic physics book at your local library or bookstore, and spend some time learning the basics of mechanics. You don't necessarily need calculus to understand the most basic formulas and concepts. But at some point, it would be good for you to pick up differential and integral calculus, to help your understanding of basic physics better.

Will you be able to take physics and calculus soon? What year are you in high school?

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berkeman

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The d stands for a differential, which is part of differential calculus. Here's a reasonable intro to differential calculus that starts with the basics:

http://en.wikipedia.org/wiki/Differential_calculus

A differential is a "change", so dp represents a change in momentum. But the differential is special, because when you write dp/dt, that means the change in momentum during a change in time, but you shrink the time interval infinitessimally small. That gives you the most accuracy, when you express dp/dt as a continuous function, just like the velocity as a function of time is continuous.

There are pretty good tutorials for mechanics, physics, calculus, etc. on the Internet. There's a good MIT video series as well... I'll see if I can find the link. It's listed over in the PF Learning Materials forum, I think.....

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berkeman

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https://www.physicsforums.com/showthread.php?t=95523

https://www.physicsforums.com/showthread.php?t=204664 (Yale's intro to Physics)

https://www.physicsforums.com/showthread.php?t=257942

https://www.physicsforums.com/showthread.php?t=209683 (ah, the MIT series plus others)

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I do greatly appreciate your help by the way its very helpful

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berkeman

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I remember a long time ago, I was trying to come up with a mechanism that would do something similar -- convert rotary motion and energy into linear motion. The problem is that for an isolated system (nothing goes in or out), momentum is conserved and cannot change. So, whatever your linear momentum is to start (p=mv), that's what you are stuck with, no matter what you do in that closed system. The only reason rockets can fly through space, is that the fuel that they burn ejects mass out the nozzle. This shoots some mass one way, and the mass of the rocket goes the other way.

So any trick that you could think of to convert isolated rotational motion into isolated linear motion, would violate the conservation of linear momentum principle. And that is extremely unlikely/impossible.

That's why it is good to learn as much real math and physics as you can, so that you don't waste any brain cycles on something that is basically impossible. That frees up brain cycles to work on hard science problems that *may* be possible, and believe me, there is plenty of room for invention and innovation in the realm of real science.

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