A simple harmonic oscillator has spring constant = 8.8N/m , amplitude = 11cm , and maximum speed 4.6 m/s. what is the speed at x=6cm?
At 6 cm deflection, the oscillator has (6/11)^2 = 29.75% of its maximum potential (spring) energy. That means it has 70.25% of its maximum kinetic energy. The Velocity is at that time sqrt(0.7025) = 83.8% of the maximum value, or 3.86 m/s
You do not need to know the spring constant to answer this.