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Java > Open Source Codes > JSci > physics > Spring


1 package JSci.physics;
2
3 import JSci.maths.vectors.AbstractDoubleVector;
4 import JSci.maths.vectors.DoubleVector;
5
6 public class Spring {
7         private final double coefficient;
8         private AbstractDoubleVector x;
9
10         /**
11         * Constructs a mechanical spring.
12         * @param coeff the spring constant.
13         */
14         public Spring(double coeff) {
15                 coefficient = coeff;
16         }
17         public void setPosition(AbstractDoubleVector pos) {
18                 x = pos;
19         }
20         public AbstractDoubleVector getPosition() {
21                 return x;
22         }
23         /**
24         * Returns the potential energy of a particle attached to this spring.
25         */
26         public double energy(AbstractClassicalParticle p) {
27                 double rr = 0.0;
28                 AbstractDoubleVector ppos = p.getPosition();
29                 for(int i=0; i<x.dimension(); i++) {
30                         final double dx = ppos.getComponent(i)-x.getComponent(i);
31                         rr += dx*dx;
32                 }
33                 return coefficient*rr/2.0;
34         }
35         public Force createForce(AbstractClassicalParticle p) {
36                 return new Force(p);
37         }
38         private class Force extends JSci.physics.Force {
39                 private final AbstractClassicalParticle p;
40                 public Force(AbstractClassicalParticle p) {
41                         this.p = p;
42                 }
43                 public AbstractDoubleVector getVector(double t) {
44                         AbstractDoubleVector ppos = p.getPosition();
45                         final double vec[] = new double[x.dimension()];
46                         for(int i=0; i<vec.length; i++)
47                                 vec[i] = -coefficient*(ppos.getComponent(i)-x.getComponent(i));
48                         return new DoubleVector(vec);
49                 }
50         }
51 }
52
53
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