1. The problem statement, all variables and given/known data A 35 kg child is jumping on a pogo stick. If the spring has a constant of 4945 N/m and it is compressed 25 cm, how high will the child bounce? Answer: 0.45 m Need help substituting the right variable. 2. Relevant equations ETi= ETf Egi + Eki + Eei = Egf + Ekf + Eef mghi + 0.5mvi2 + 0.5ksi2 = mghf + 0.5mvf2 + 0.5ksf2 3. The attempt at a solution The real problem I have is setting the defined variables; everything I can solve for. I used trial and error and got 0.45 but I NEED TO KNOW WHY I use the variables (magnitudes in the right place)! m = 35 kg k = 4954 N/m g = 9.8 m/s² si = 0 m sf = 0.37 m hi = 0 m hf = ? vi = 0 m/s² vf = 0 m/s² I rearranged and solved and I got -0.45 m, some please tell me where what variables I have to substitute correctly! Thank you!