Newtons second law

General
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I’m trying (and failing high school maths) to work out how to apply gravity to two xojo.point objects. This is how far I have got.

Created two points
dim v1 as new Xojo.Core.Point(x,y)
dim v2 as new Xojo.Core.Point(x1,y1)

worked out the distance between then
dim distance as double=v1.DistanceTo(v2)

worked out the angle in relation to them
dim angle as double=(((atan2(y1 - y, x1 - x)) * 180 )/ 3.14159265)

ok this is where it goes wrong ( i think , i,m guessing i need two forces ? )

dim force as double = log(distance*mass) ’ Think I should be using inverse log here, but I cant find a log10 function in Xojo

then i apply the calculation
x=x+cos(angle*0.0174533)force
y=y+sin(angle0.0174533)*force

Any mathematical wizards out there want to take up the challenge… I’ve looked at ABPE and could not work out if he was actually using NL.

2 
func Log10(x as double) as double
return log(x)/log(10)
end function

What Xojo defines as LOG is the Natural Log, elsewhere designated as “ln” or “log2”

3

What is the mass?
Seems to be uninitialised and therefore zero

Force = mass*acceleration

7

you were correct to remove the *0.017xx as your were already stating ANGLE as radians.
however, and I haven’t checked… but are you sure you don’t have this inverted?

dim angle as double=(((atan2(y1 - y, x1 - x)) * 180 )/ 3.14159265)

or do you even need the 180 and Pi? since Atan2 is also radians

dim angle as double=atan2(y1 - y, x1 - x)
8

Not sure exactly what you’re trying to calculate. If it’s gravitational force, then I don’t know how the log() function manages to get in there. The gravitational force between two objects is simply:
F=gm1m2/r^2
where
g is the gravitational constant 6.674e-11 (SI units)
m1 and m2 are the masses of the objects,
r is the distance separating them,
The direction of the force is the direction of the line joining the two points. So the angle ? is given as:
? = atan2(p1y-p2y,p1x-p2x)
where p1x,p1y,p2x and p2y are the x and y coordinates of points p1 and p2.
Once you know force, then acceleration is given by:
a=F/m
where F is force, m is the mass of the object, and a is acceleration.
To convert the acceleration into separate x and y components you use the standard trigonometric conversions.
ay=a sin(?)
ax=a cos(?)

9

Adding to Robert’s post:

And to calculate the new position and velocity of the objects you have to take into account their current velocity.

I may not be understanding properly what you are doing though.

Julen

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