1. The problem statement, all variables and given/known data Find the stiffness of the spring in a child's pogo stick if the child has a mass of 35kg and bounces once every 2.0 seconds. T = 2.0 seconds m = 35kg 2. Relevant equations T = 2π√(m/k) 3. The attempt at a solution Using the above, I figured k = mπ2 which worked out to be 345.44 This problem didn't have an answer in the back of the book. I saw a similar equation for frequency so I used the frequency/period relationship to formulate the above equation. I figured I should ask for a check in case I assumed wrong.