I have the question "Calculate the velocity of the same mass on a spring when it is at equilibrium."
This is related to the previous question "A mass is oscillating vertically on a spring, with a maximum amplitude of 10.0cm. If it has a frequency of oscillation of 5.0Hz. Find its velocity at 5.0cm from equilibrium."
For which I got V = 2.7 ms^-1.
I am not sure however how to calculate the velocity when the mass is at equilibrium.
Although this belongs to Physics SE but I will tell you how to do it. Equilibrium in motion is when the net forces on the body=0. And in simple harmonic motion it is at x=0, since at that point, the spring force and weight of the object are equal and opposite i.e Fnet=0. And recall that velocity of the object is maximum at the equlibrium postion(you can write equation of the above motion and differentiate it to get the expression of velocity and then check for velocity at x=0). You will find that maximum velocity =Amplitude*angular frequency where angular frequency =2*pi*frequency of oscillation. So your answer will be 10*2*pi*5 = 100*pi cm/s or pi m/s.