// The stiffness of the spring
// A bigger value makes the bounce animation faster and a short value makes it slower"
float k = 100;

// The compression of the spring
float x = 0.5;

// The velocity of the spring each frame
float v = 0;

void Update () {
    float F = -k * this.compression; // F = kx
    this.v += F * Time.deltaTime; // v = at
    this.x += this.v * Time.deltaTime; // x = vt

    this.transform.localScale = new Vector3(1 + this.x, 1 - this.x, 1);
}