1. The problem statement, all variables and given/known Spring constant of trampoline and cradle 2. Relevant equations k=F/x 3. The attempt at a solution I think a trampoline should have a low spring constant so that the extension is bigger. Is this correct? For cradle, in my opinion, it should have a low spring constant too so that the extension is bigger and the babies are able to sleep soundly. However, according to the answers given, the spring of a cradle has high spring constant. Does anyone know which one is correct? If yes, please kindly explain to me.