Suppose a point mass m is attached to one end of a spring of spring constant k. The other end of the spring is fixed on a massless cart that is being moved uniformly on a horizontal plane by an external device with speed v0. If the position q of the mass in the stationary system is taken as the generalized coordinate, then the Lagrangian of the system is
1. m2˙q2−k2(q−v0t)
2. m2˙q2−k2(q−v0t)2
3. m2˙q2+k2(q−v0t)
4. m2˙q2+k2(q−v0t)2