Answer:
3.At equilibrium, its instantaneous velocity is at maximum
Explanation:
The motion of a mass on the end of a spring is a simple harmonic motion. In a simple harmonic motion, the total mechanical energy of the system is constant, and it is sum of the elastic potential energy (U) and the kinetic energy of the mass (K):
where
k is the spring constant
x is the displacement of the spring from equilibrium
m is the mass
v is the speed
As we see from the formula, since the total energy E is constant, when the displacement (x) increases, the speed (v) increases, and viceversa. Therefore, when the mass is at its equilibrium position (which corresponds to x=0), the velocity of the mass will be maximum.