When preparing the pistol for a shot, the spring with a stiffness of 1kN / m stretched by 3 cm.

When preparing the pistol for a shot, the spring with a stiffness of 1kN / m stretched by 3 cm. What speed does a bullet weighing 45g acquire when moving in a horizontal direction?

k = 1 kN / m = 1000 N / m.
x = 3 cm = 0.03 m.
m = 45 g = 0.045 kg.
V -?
If the losses of mechanical energy during a shot are neglected, then the law of conservation of total mechanical energy is valid.
All the potential energy of the compressed spring, En, is converted into the kinetic energy of the body’s motion Ek: En = Ek.
En = k * x ^ 2/2.
Ek = m * V ^ 2/2.
k * x ^ 2/2 = m * V ^ 2/2.
V2 = k * x ^ 2 / m.
V = x * √ k / √m.
V = 0.03 m * √1000 N / m / √0.045 kg = 4.5 m / s.
Answer: at the moment of firing, the ball acquires a speed of V = 4.5 m / s.