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package main
import (
"math"
)
// forces_acting calculates the force inbetween the two given stars s1 and s2
// The function return the force
func forces_acting(s1 star, s2 star) force {
// Gravitational constant
var G float64 = 6.674 * math.Pow(10, -11)
// Distance between the stars
var r21 float64 = math.Sqrt(math.Pow(s2.c.x - s1.c.x, 2) + math.Pow(s2.c.y - s1.c.y, 2))
// Unit vector pointing from s1 to s2
rhat := force{s2.c.x - s1.c.x, s2.c.y - s1.c.y}
// Calculate how strong the star is affected
var F_scalar float64 = G * (s1.mass * s2.mass) / math.Pow(math.Abs(r21), 2)
// Calculate the overall force by combining the scalar and the vector
var Fx float64 = F_scalar * rhat.x
var Fy float64 = F_scalar * rhat.y
// Pack the forces in a force structur
F := force{Fx, Fy}
return F
}
// forces calculates the forces acting in between a given star and all the other stars in a given array.
func forces(stars_arr []star, nr int) {
// Iterate over all the stars in the stars_arr
for index, _ := range stars_arr {
// If the current star is not the star itself
if index != nr {
// generate a new force and add it to the overall force of the star
fa := force_acting(stars_arr[nr], stars_arr[index])
stars_arr[nr].f.x += fa.x
stars_arr[nr].f.y += fa.y
}
}
}
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