# Help with Math formula's in VB.net



## sdeyoung1974 (Apr 8, 2005)

I need to create a program that will calculate the velocity of a ball being thrown in the air. I'm having a little trouble figuring out the math formula. It goes like this.

A ball is thrown in the air with an initial velocity of 50 feet per second and an initial height of 5 feet. How high will the ball be after 3 seconds? The height after t seconds is given by the following expression -16t² + vt + h where v is the initial velocity and h is the initial height.

Can anyone make sense of this? Any help would be greatly appreciated.

TIA


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## pvc_ (Feb 18, 2008)

h (3) = -16(9) + 50(3) + 5
h (3) = 11


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## sdeyoung1974 (Apr 8, 2005)

Sorry, but could you explain the equation a little? Physics is not my thing...


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## pvc_ (Feb 18, 2008)

the problem is already giving you the equation, You only have to plug in the values and that's what I did. I don't even know why you need to write a program for this because all the values are already given to you and you just have to solve the problem.

If you really need to program this, you'd have to create a variable for each of the variables (v, t, h) and just ask the user for those values and run the same equation. It's really that simple.


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## sdeyoung1974 (Apr 8, 2005)

I know it's simple. I'm just trying to understand the equation I guess.. 

-16t² + vt + h

like what does -16t² stand for?
what is vt?
I understand that h is height, that much I know, lol

As far as why I'm writing this app is that it's for school.. : )


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## pvc_ (Feb 18, 2008)

-16 is just a constant set by the given equation.
t² = t * t (time to the power of 2)
v = velocity

It's just an arbitary equation set by the problem. Based on the size, or weight of the ball they have come up with an equation and they want you to plug-in the values to calculate the height.


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## geekman3232 (Oct 1, 2009)

pvc is close, but he is wrong about it being specific to this problem. It is far from arbitrary. The equation is derived from the acceleration of gravity. The acceleration, a, of gravity on the earth is:
























This is true for every object on earth, a feather, a bowling ball, anything. To derive the equation for position, we must first derive the equation for velocity. This is done through integration (its calculus) which is basically finding the area under the curve.

















This essentially is translated to the velocity at time t is the acceleration of gravity times the time at that instant plus the initial velocity. To find the position we integrate the velocity equation:










This means that the position at time t is half the acceleration of gravity times the time at that instant squared plus the initial velocity times time plus the initial position.

Hope this helps you understand the equation a little better. You don't have to understand the calculus, but just understand that the height is related to acceleration of gravity. Feel free to ask any questions.


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## pvc_ (Feb 18, 2008)

We all know a feather does not fall at the same speed as a ball because of air resistance. In this case, I guess we can assume air resistance is not significant enough to be considered.

But anyway, I didn't know about a(t) = - 32 ft/(sec ^ 2)
since I've mostly dealt with its metric form (9.8 m /(sec ^ 2))


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## geekman3232 (Oct 1, 2009)

> We all know a feather does not fall at the same speed as a ball because of air resistance. In this case, I guess we can assume air resistance is not significant enough to be considered.


Yeah, I assumed that is correct as well. I guessed sdeyoung is doing this around the high school level, and I know I didn't really see problems dealing with drag until college.


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## sdeyoung1974 (Apr 8, 2005)

Actually it's a program I was writing for college but it's not required that I know the math. I was just curious and thought it was something I should know : )
Thanks guys!


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