1. A girl swings on a playground swing in such a way that at her highest point she is 3 m from the ground, while at her lowest point she is 0.5m from the ground. The acceleration of gravity is 9.8m/s^2. What is her maximum speed? Answer in units of m/s. 2. 1/2mVf^2 + mgyf = 1/2mVi^2 + mgyi I made initial velocity to equal zero. 3. [Vf= (mghi - mghf)/ (1/2m)]^(1/2) When I do this... I endup square rooting a negative number. What am I doing wrong?