如何求解方程并以正确的方式保存

我是c++的新手。所以实际上，我会试图找出每个时间步长（dt=0.00001）中的总力、速度、位置和总时间，并从求解简单方程中保存myfile1、myfile2、myfile3、myfile4。我正面临着找出确切价值的问题。当我运行程序时，会发现分段错误。那么我该如何解决这个问题呢？我附上下面的程序：有人能帮我吗？

//C++ programming for selection random number
#include <cstdlib>
#include <iostream>
#include <fstream>
#include <ctime>
#include <sstream>
#include <string>
#include <iomanip>
#include <cmath>

//%stifness
double kp=1000;
//%gravitational
double g=-9.81;

    double x[10000], y[10000], z[10000];
    double Fx[10000],Fy[10000],  Fz[10000];
    double vx[10000],vy[10000], vz[10000] ;
    double ax[10000],ay[10000], az[10000] ;
    double force[10000];
    const double PI=4.0*atan(1.0); 
    using namespace std;
int main()
{
    srand((unsigned) time(NULL));
//open output file
    ofstream myfile1;
    myfile1.open("1.dat");
    ofstream myfile2;
    myfile2.open("2.dat");
    ofstream myfile3;
    myfile3.open("3.dat");
    ofstream myfile4;
    myfile4.open("4.dat");

// %particle parameter
double  dt=1e-5;
double Ntimestep=1000;
//particle properties
    double R=0.003;
    double Dens=2600;
        int npart=1;
//Particle Creation 
        double Mass=(Dens*4*PI*(pow(R,3))/3);    //m=(4/3)* Dens*Pi*R^3
        cout<<"Mass="<< Mass<<endl;
//initial position of the particle
        x[0]=0;
            y[0] =0.01;
            z[0] =0;
// movement of the particle
// Particle initial velocity and forces
     Fx[0]=0;
     Fy[0]=0; 
     Fz[0]=0;
     vx[0]=0;
     vy[0]=-0.5;
     vz[0]=0;
     force[0]=0;
// Relation between dashport coefficient and coefficient of restitution
     double exp=0.9;
     double lnexp=0.10536;
     double Eta= ((2*sqrt(Mass*kp)*lnexp)/(sqrt(pow(PI,2)+pow(lnexp,2))));
//Time step
    int t=0;
for (int i=0;i<Ntimestep;i++)
{
// calculate particle to wall contact force
       if (y[i]<R)
            {
                Fy[i]=(-kp*(y[i]-R))-Eta*vy[i];
            }
// Calculate initial acceleration
        ay[i]=(Fy[i]/Mass)+g;
//force[i]+=force[1];
        force[i+1]=ay[i]*Mass;
        //cout<<"Total_Force="<<force<<endl;
// update valocity and displacement/location
    vy[i+1]=(vy[i]+(ay[i]*dt));
    y[i+1]=y[i]+vy[i]*dt+0.5*ay[i]*pow(dt,2);
    Fy[i]=0;
    t=t+1;
     double time=t*dt;

//...............output/save file..............................
cout<<"Total force="<<force<<endl;
myfile1<<"Total force="<<force<<endl;
cout<<"velocity="<<vy<<endl;
myfile2<<"velocity="<<vy<<endl;
cout<<"location="<<y<<endl;
myfile3<<"location="<<y<<endl;
cout<<"Total time"<<time<<endl;
myfile4<<"Total time="<<time<<endl;
}

//system ("PAUSE");
    cin.ignore();
    cin.get();
    myfile1.close();
    myfile2.close();
    myfile3.close();
    myfile4.close();

    return 0;
}