particle.h

class Particle {
public:
    Particle();
    Particle(double mass, const Vector2D &acceleration, const Vector2D &velocity, const Vector2D &position);

    bool operator==(const Particle &rhs) const;
    bool operator!=(const Particle &rhs) const;

    double getMass() const;

    const Vector2D &getAcceleration() const;
    void setAcceleration(const Vector2D &acceleration);

    const Vector2D &getVelocity() const;
    void setVelocity(const Vector2D &velocity);

    const Vector2D &getPosition() const;
    void setPosition(const Vector2D &position);

private:
    static size_t IDCounter;

    size_t id;
    double mass;
    Vector2D acceleration;
    Vector2D velocity;
    Vector2D position;
};