A block is connected between two springs on a frictionless horizontally level track. The other end of each spring is respectively anchored to a vertical pin set at opposite ends of the track. The spring constant for one spring is k = 100N/m and the mass of the block is 0.300 kg. If the period of oscillation T is 0.21 s, what is the spring constant of the other spring?

Find the series k from the mass and period of oscillation. w= 2PIf=2PI/T

w= sqrt (k/m)

Then, having that k

1/k= 1/k1 + 1/k2

solve for k2